Revert "[SLPV] Recognize vectorizable intrinsics during SLP vectorization ..."

This reverts commit r200576.  It broke 32-bit self-host builds by
vectorizing two calls to @llvm.bswap.i64, which we then fail to expand.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200602 91177308-0d34-0410-b5e6-96231b3b80d8