[X86][SSE] Replace (VSRLI (VSRAI X, Y), 31) -> (VSRLI X, 31) fold.

This fold was incredibly specific - replace with a SimplifyDemandedBits fold to remove a VSRAI if only the original sign bit is demanded (its guaranteed to stay the same).

Test change is merely a rescheduling.

llvm-svn: 349459