Revert "[VirtRegRewriter] Avoid clobbering registers when expanding copy bundles"

There's an msan failure:

  http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-fast/builds/19549

This reverts r334750.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@334754 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed