RISC-V: Enable and adjust the testsuite for XTheadVector.

RISC-V: Enable and adjust the testsuite for XTheadVector.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/rvv.exp: Enable testsuite of
	XTheadVector.
	* gcc.target/riscv/rvv/xtheadvector/pr114194.c: Adjust correctly.
	* gcc.target/riscv/rvv/xtheadvector/prefix.c: Likewise.
	* gcc.target/riscv/rvv/xtheadvector/vlb-vsb.c: Likewise.
	* gcc.target/riscv/rvv/xtheadvector/vlbu-vsb.c: Likewise.
	* gcc.target/riscv/rvv/xtheadvector/vlh-vsh.c: Likewise.
	* gcc.target/riscv/rvv/xtheadvector/vlhu-vsh.c: Likewise.
	* gcc.target/riscv/rvv/xtheadvector/vlw-vsw.c: Likewise.
	* gcc.target/riscv/rvv/xtheadvector/vlwu-vsw.c: Likewise.