[AMDGPU] Do not combine dpp mov reading physregs

We cannot be sure physregs will stay unchanged.

Differential Revision: https://reviews.llvm.org/D69065

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@375033 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed