[llvm] Revert "Update amdgpu_gfx functions to use s0-s3 for inreg SGPR arguments on targets using scratch instructions for stack #78226" (PR #86273)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> We need to re-visit the patch, but apparently we only want to have s0-s3 as argument registers if we don't need them as RSrc registers.

Yes, that was the point. It's just wasted space as-is 


https://github.com/llvm/llvm-project/pull/86273