[llvm] [WIP][AMDGPU] Make `getAssumedAddrSpace` return AS1 for pointer kernel arguments (PR #137488)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

Can we delete the AMDGPUPromoteKernelArguments pass after this (but really clang should be fixed, we shouldn't have to do this)

https://github.com/llvm/llvm-project/pull/137488