[llvm] [AMDGPU] Infer Alignments after Inferring AddressSpaces (PR #69776)

[Matt Arsenault via llvm-commits]

arsenm wrote:

getOrEnforceKnownAlignment should just handle addspacecast (at least for integral address spaces). I don't want to add another pass run just for this 

https://github.com/llvm/llvm-project/pull/69776