RISC-V: Add FNMS floating-point VLS tests

Add tests and committed.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/autovec/vls/def.h: Add FNMS VLS modes tests.
	* gcc.target/riscv/rvv/autovec/vls/fnms-1.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/fnms-2.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/fnms-3.c: New test.