RISC-V: Support VLS unary floating-point patterns

Extend current VLA patterns with VLS modes.

Regression all passed.

gcc/ChangeLog:

	* config/riscv/autovec.md: Extend VLS modes.
	* config/riscv/vector.md: Ditto.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/autovec/vls/def.h: Add unary test.
	* gcc.target/riscv/rvv/autovec/vls/neg-2.c: New test.