RISC-V: Change fnms testcases assertion to xfail

RISC-V: Change fnms testcases assertion to xfail

Hi,

This patch fixes inappropriate assertions in fnms testcases since
we want to generate .COND_FNMS but actually generate .FNMS + .VCOND_MASK.
A patch to do this optimization will follow.

Best,
Lehua

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/autovec/cond/cond_fms_fnms-1.c: Adjust.
	* gcc.target/riscv/rvv/autovec/cond/cond_fms_fnms-2.c: Ditto.
	* gcc.target/riscv/rvv/autovec/cond/cond_fms_fnms-3.c: Ditto.
	* gcc.target/riscv/rvv/autovec/cond/cond_fms_fnms-4.c: Ditto.
	* gcc.target/riscv/rvv/autovec/cond/cond_fms_fnms-5.c: Ditto.
	* gcc.target/riscv/rvv/autovec/cond/cond_fms_fnms-6.c: Ditto.