[X86][SSE] Reuse zeroable element mask in SSE4A EXTRQ/INSERTQ vector shuffle lowering. NFCI

Don't regenerate a zeroable element mask with computeZeroableShuffleElements when its already available.

llvm-svn: 286043
GitOrigin-RevId: 9f0afc6ae19422094dd37eab592c491a74e07187
1 file changed