[llvm] AMDGPU/GlobalISel: Add regbanklegalize rules for load and store (PR #153176)

[Pierre van Houtryve via llvm-commits]

https://github.com/Pierre-vh approved this pull request.

I think there is no need to hold this back longer, I just have some small nits

https://github.com/llvm/llvm-project/pull/153176