[llvm] [AMDGPU] Add & use amdgcn-verify-memory-legalizer (PR #78697)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

I think we can just drop the -verify-machineinstrs in these and most tests. They are still run in EXPENSIVE_CHECKS builds 

https://github.com/llvm/llvm-project/pull/78697