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

[Shilei Tian via llvm-commits]

shiltian wrote:

> Can we delete the AMDGPUPromoteKernelArguments pass after this

Yes, that's the plan.

>  (but really clang should be fixed, we shouldn't have to do this)

And this is also in the TODO list.

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