[llvm] [AMDGPU] Folding imm offset in more cases for scratch access (PR #70634)

[Nicolai Hähnle via llvm-commits]

https://github.com/nhaehnle commented:

I don't know. The whole `CheckBothOperands` thing seems fragile to me and as if something wasn't quite right yet. See also the inline comments.

https://github.com/llvm/llvm-project/pull/70634