[x86] Unbreak SSE1 with the new vector shuffle lowering. We can't widen
element types to form illegal vector types.

I've added a special SSE1 test case here that makes sure we don't break
this going forward.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218974 91177308-0d34-0410-b5e6-96231b3b80d8