[llvm] [AMDGPULowerBufferFatPointers] Expand const exprs using fat pointers (PR #95558)

[Krzysztof Drewniak via llvm-commits]

https://github.com/krzysz00 approved this pull request.

This all makes sense and it makes the code a lot cleaner!

https://github.com/llvm/llvm-project/pull/95558