Revert "Optimize shufflevector that copies an i64/f64 and zeros the rest."

This reverts commit 207992. I misread the phab number on the LGTM.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207993 91177308-0d34-0410-b5e6-96231b3b80d8