RISC-V: Add ternary constraint tests

RISC-V: Add ternary constraint tests

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/base/ternop_vv_constraint-1.c: New test.
	* gcc.target/riscv/rvv/base/ternop_vv_constraint-2.c: New test.
	* gcc.target/riscv/rvv/base/ternop_vx_constraint-1.c: New test.
	* gcc.target/riscv/rvv/base/ternop_vx_constraint-2.c: New test.
	* gcc.target/riscv/rvv/base/ternop_vx_constraint-3.c: New test.
	* gcc.target/riscv/rvv/base/ternop_vx_constraint-4.c: New test.
	* gcc.target/riscv/rvv/base/ternop_vx_constraint-5.c: New test.
	* gcc.target/riscv/rvv/base/ternop_vx_constraint-6.c: New test.
	* gcc.target/riscv/rvv/base/ternop_vx_constraint-7.c: New test.