LoongArch: Remove masking process for operand 3 of xvpermi.q.

LoongArch: Remove masking process for operand 3 of xvpermi.q.

The behavior of non-zero unused bits in xvpermi.q instruction's
third operand is undefined on LoongArch, according to our
discussion (https://github.com/llvm/llvm-project/pull/83540),
we think that keeping original insn operand as unmodified
state is better solution.

This patch partially reverts 7b158e036a95b1ab40793dd53bed7dbd770ffdaf.

gcc/ChangeLog:

	* config/loongarch/lasx.md (lasx_xvpermi_q_<LASX:mode>):
	Remove masking of operand 3.

gcc/testsuite/ChangeLog:

	* gcc.target/loongarch/vector/lasx/lasx-xvpermi_q.c:
	Reposition operand 3's value into instruction's defined accept range.