AMDGPU: Recompute scc liveness

The various scalar bit operations set SCC,
so one is erased or moved it needs to be recomputed.
Not sure why the existing tests don't fail on this.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312819 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed