[X86] Remove isel patterns that look for (vzext_movl (scalar_to_vector (load)))

I believe these all get canonicalized to vzext_movl. The only case where that wasn't true was when the load was loadi32 and the load was an extload aligned to 32 bits. But that was fixed in r364207.

Differential Revision: https://reviews.llvm.org/D63701

llvm-svn: 364337