[AMDGPU] fix atomic_optimizations_buffer.ll test after DPP combiner was enabled by default.

Related commits: rL353691, rL353703.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@353717 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed