RISC-V:Add float16 tuple type abi

RISC-V:Add float16 tuple type abi

gcc/ChangeLog:

	* config/riscv/vector.md: Add float16 attr at sew、vlmul and ratio.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/base/abi-10.c: Add float16 tuple type case.
	* gcc.target/riscv/rvv/base/abi-11.c: Ditto.
	* gcc.target/riscv/rvv/base/abi-12.c: Ditto.
	* gcc.target/riscv/rvv/base/abi-15.c: Ditto.
	* gcc.target/riscv/rvv/base/abi-8.c: Ditto.
	* gcc.target/riscv/rvv/base/abi-9.c: Ditto.
	* gcc.target/riscv/rvv/base/abi-17.c: New test.
	* gcc.target/riscv/rvv/base/abi-18.c: New test.