[A57FPLoadBalancing] Modify r217689 - actually we do need to check defs

... Just make sure we check uses first so we see the kill first. It
turns out ignoring defs gives some pretty nasty runtime failures.
I'm certain this is the fix but I'm still reducing a testcase.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217735 91177308-0d34-0410-b5e6-96231b3b80d8