[X86] XFormVExtractWithShuffleIntoLoad - handle shuffle mask scaling

If the target shuffle mask is from a wider type, attempt to scale the mask so that the extraction can attempt to peek through.

Fixes the regression mentioned in rL368662

Reapplying this as rL368308 had to be reverted as part of rL368660 to revert rL368276

llvm-svn: 368663