[llvm] Update amdgpu_gfx functions to use s0-s3 for inreg SGPR arguments on targets using scratch instructions for stack (PR #78553)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> > For clarity, I see this warning for all tests, i.e, I am unable to use any of those utility commands with the same issue as mentioned in the above comment.
> 
> @arsenm Can you let me know the cause for this?

Some tests are not autogenerated and will need manually updating (or updating with update_mir_test_checks). The warning is expected. You should see it working on some of them 

https://github.com/llvm/llvm-project/pull/78553