Revert "[x86] Fold extract_vector_elt of a load into the Load's address computation."

There's a bug where this can create cycles in the DAG. It will take a bit
to fix, so I'm backing it out for now.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213339 91177308-0d34-0410-b5e6-96231b3b80d8