[llvm] [AMDGPU][SIPreEmitPeephole] mustRetainExeczBranch: accept memory instructions in the "then" block (PR #109995)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

Probably should benchmark this first. I think @cdevadas added this 

https://github.com/llvm/llvm-project/pull/109995