[AMDGPU] Allow DPP combiner to work with REG_SEQUENCE

Differential Revision: https://reviews.llvm.org/D68828

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@374908 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed