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

[Rajveer Singh Bharadwaj via llvm-commits]

Rajveer100 wrote:

@arsenm 
Let me know if these were the intended changes to be done.

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