RISC-V: Support VLS modes mask operations

RISC-V: Support VLS modes mask operations

This patch support mask operations (comparison and logical).

This patch reduce these FAILs of "vect" testsuite:
FAIL: gcc.dg/vect/vect-bic-bitmask-12.c -flto -ffat-lto-objects  scan-tree-dump dce7 "<=\\s*.+{ 255,.+}"
FAIL: gcc.dg/vect/vect-bic-bitmask-12.c scan-tree-dump dce7 "<=\\s*.+{ 255,.+}"
FAIL: gcc.dg/vect/vect-bic-bitmask-23.c -flto -ffat-lto-objects  scan-tree-dump dce7 "<=\\s*.+{ 255, 15, 1, 65535 }"
FAIL: gcc.dg/vect/vect-bic-bitmask-23.c scan-tree-dump dce7 "<=\\s*.+{ 255, 15, 1, 65535 }"

Full regression passed (with reducing 4 FAILs).

gcc/ChangeLog:

	* config/riscv/autovec-opt.md: Add VLS mask modes.
	* config/riscv/autovec.md (@vcond_mask_<mode><vm>): Remove @.
	(vcond_mask_<mode><vm>): Add VLS mask modes.
	* config/riscv/vector.md: Ditto.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/autovec/vls/def.h: Add VLS tests.
	* gcc.target/riscv/rvv/autovec/vls/cmp-1.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/cmp-2.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/cmp-3.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/cmp-4.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/cmp-5.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/cmp-6.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/mask-1.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/mask-2.c: New test.
	* gcc.target/riscv/rvv/autovec/vls/mask-3.c: New test.