RISC-V: Add vdiv.vx C++ API test.

RISC-V: Add vdiv.vx C++ API test.

gcc/testsuite/ChangeLog:

	* g++.target/riscv/rvv/base/vdiv_vx_mu_rv32-1.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_mu_rv32-2.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_mu_rv32-3.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_mu_rv64-1.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_mu_rv64-2.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_mu_rv64-3.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_rv32-1.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_rv32-2.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_rv32-3.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_rv64-1.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_rv64-2.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_rv64-3.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_tu_rv32-1.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_tu_rv32-2.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_tu_rv32-3.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_tu_rv64-1.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_tu_rv64-2.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_tu_rv64-3.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_tum_rv32-1.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_tum_rv32-2.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_tum_rv32-3.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_tum_rv64-1.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_tum_rv64-2.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_tum_rv64-3.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_tumu_rv32-1.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_tumu_rv32-2.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_tumu_rv32-3.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_tumu_rv64-1.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_tumu_rv64-2.C: New test.
	* g++.target/riscv/rvv/base/vdiv_vx_tumu_rv64-3.C: New test.