RISC-V: Add vmax.vx C++ API tests.

RISC-V: Add vmax.vx C++ API tests.

gcc/testsuite/ChangeLog:

	* g++.target/riscv/rvv/base/vmax_vx_mu_rv32-1.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_mu_rv32-2.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_mu_rv32-3.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_mu_rv64-1.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_mu_rv64-2.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_mu_rv64-3.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_rv32-1.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_rv32-2.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_rv32-3.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_rv64-1.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_rv64-2.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_rv64-3.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_tu_rv32-1.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_tu_rv32-2.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_tu_rv32-3.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_tu_rv64-1.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_tu_rv64-2.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_tu_rv64-3.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_tum_rv32-1.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_tum_rv32-2.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_tum_rv32-3.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_tum_rv64-1.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_tum_rv64-2.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_tum_rv64-3.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_tumu_rv32-1.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_tumu_rv32-2.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_tumu_rv32-3.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_tumu_rv64-1.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_tumu_rv64-2.C: New test.
	* g++.target/riscv/rvv/base/vmax_vx_tumu_rv64-3.C: New test.