RISC-V: Add vrsub.vx C API tests

RISC-V: Add vrsub.vx C API tests

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/base/vrsub_vx_m_rv32-1.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_m_rv32-2.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_m_rv32-3.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_m_rv64-1.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_m_rv64-2.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_m_rv64-3.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_mu_rv32-1.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_mu_rv32-2.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_mu_rv32-3.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_mu_rv64-1.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_mu_rv64-2.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_mu_rv64-3.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_rv32-1.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_rv32-2.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_rv32-3.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_rv64-1.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_rv64-2.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_rv64-3.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_tu_rv32-1.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_tu_rv32-2.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_tu_rv32-3.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_tu_rv64-1.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_tu_rv64-2.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_tu_rv64-3.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_tum_rv32-1.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_tum_rv32-2.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_tum_rv32-3.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_tum_rv64-1.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_tum_rv64-2.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_tum_rv64-3.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_tumu_rv32-1.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_tumu_rv32-2.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_tumu_rv32-3.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_tumu_rv64-1.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_tumu_rv64-2.c: New test.
	* gcc.target/riscv/rvv/base/vrsub_vx_tumu_rv64-3.c: New test.