RISC-V: Support VLS reduction

Notice previous VLS reduction patch is missing some codes which cause multiple ICE:
FAIL: gcc.target/riscv/rvv/autovec/reduc/reduc_run-2.c (internal compiler error: in code_for_pred, at ./insn-opinit.h:1560)
FAIL: gcc.target/riscv/rvv/autovec/reduc/reduc_run-2.c (internal compiler error: in code_for_pred, at ./insn-opinit.h:1560)
FAIL: gcc.target/riscv/rvv/autovec/reduc/reduc_run-2.c (internal compiler error: in code_for_pred, at ./insn-opinit.h:1560)
FAIL: gcc.target/riscv/rvv/autovec/reduc/reduc_run-2.c (internal compiler error: in code_for_pred, at ./insn-opinit.h:1560)
FAIL: gcc.target/riscv/rvv/autovec/reduc/reduc_run-2.c (internal compiler error: in code_for_pred, at ./insn-opinit.h:1560)
FAIL: gcc.target/riscv/rvv/autovec/reduc/reduc_run-2.c (internal compiler error: in code_for_pred, at ./insn-opinit.h:1560)
FAIL: gcc.target/riscv/rvv/autovec/reduc/reduc_run-2.c (internal compiler error: in code_for_pred, at ./insn-opinit.h:1560)
FAIL: gcc.target/riscv/rvv/autovec/reduc/reduc_run-2.c (internal compiler error: in code_for_pred, at ./insn-opinit.h:1560)
FAIL: gcc.target/riscv/rvv/autovec/reduc/reduc_run-2.c (test for excess errors)
FAIL: gcc.target/riscv/rvv/autovec/reduc/reduc_run-2.c (test for excess errors)
FAIL: gcc.target/riscv/rvv/autovec/reduc/reduc_run-2.c (test for excess errors)
FAIL: gcc.target/riscv/rvv/autovec/reduc/reduc_run-2.c (test for excess errors)
FAIL: gcc.target/riscv/rvv/autovec/reduc/reduc_run-2.c (test for excess errors)
FAIL: gcc.target/riscv/rvv/autovec/reduc/reduc_run-2.c (test for excess errors)
FAIL: gcc.target/riscv/rvv/autovec/reduc/reduc_run-2.c (test for excess errors)
FAIL: gcc.target/riscv/rvv/autovec/reduc/reduc_run-2.c (test for excess errors)
FAIL: gcc.target/riscv/rvv/autovec/vls-vlmax/vec_extract-run.c -std=c99 -O3 -ftree-vectorize --param riscv-autovec-preference=fixed-vlmax (test for excess errors)
FAIL: gcc.target/riscv/rvv/autovec/vls-vlmax/vec_extract-runu.c -std=c99 -O3 -ftree-vectorize --param riscv-autovec-preference=fixed-vlmax (test for excess errors)
FAIL: gcc.target/riscv/rvv/autovec/vls-vlmax/vec_set-run.c -std=c99 -O3 -ftree-vectorize --param riscv-autovec-preference=fixed-vlmax (test for excess errors)
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-1.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredsum\\.vs 22
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-10.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredmax\\.vs 9
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-10.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredmaxu\\.vs 9
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-10.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredmin\\.vs 9
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-10.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredminu\\.vs 9
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-11.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredmax\\.vs 8
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-11.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredmaxu\\.vs 8
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-11.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredmin\\.vs 8
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-11.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredminu\\.vs 8
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-12.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vfredmax\\.vs 10
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-12.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vfredmin\\.vs 10
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-13.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vfredmax\\.vs 9
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-13.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vfredmin\\.vs 9
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-14.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vfredmax\\.vs 8
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-14.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vfredmin\\.vs 8
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-15.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredand\\.vs 22
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-15.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredor\\.vs 22
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-15.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredxor\\.vs 22
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-16.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredand\\.vs 20
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-16.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredor\\.vs 20
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-16.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredxor\\.vs 20
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-17.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredand\\.vs 18
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-17.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredor\\.vs 18
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-17.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredxor\\.vs 18
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-18.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredand\\.vs 16
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-18.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredor\\.vs 16
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-18.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredxor\\.vs 16
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-19.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable (internal compiler error: in code_for_pred, at ./insn-opinit.h:1560)
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-19.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable (test for excess errors)
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-2.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredsum\\.vs 20
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-20.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable (internal compiler error: in code_for_pred, at ./insn-opinit.h:1560)
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-20.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable (test for excess errors)
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-21.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable (internal compiler error: in code_for_pred, at ./insn-opinit.h:1560)
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-21.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable (test for excess errors)
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-3.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredsum\\.vs 18
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-4.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredsum\\.vs 16
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-5.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vfredusum\\.vs 10
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-6.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vfredusum\\.vs 9
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-7.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vfredusum\\.vs 8
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-8.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredmax\\.vs 11
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-8.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredmaxu\\.vs 11
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-8.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredmin\\.vs 11
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-8.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredminu\\.vs 11
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-9.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredmax\\.vs 10
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-9.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredmaxu\\.vs 10
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-9.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredmin\\.vs 10
FAIL: gcc.target/riscv/rvv/autovec/vls/reduc-9.c -O3 -ftree-vectorize --param riscv-autovec-preference=scalable  scan-assembler-times vredminu\\.vs 10

Committed.

gcc/ChangeLog:

	* config/riscv/autovec.md: Add VLS modes.
	* config/riscv/vector-iterators.md: Ditto.
	* config/riscv/vector.md: Ditto.