[X86][SSE] Check for lane crossing shuffles before trying to combine to PSHUFB

Removes a return-on-fail that was making it tricky to add other variable mask shuffles.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@275262 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed