[llvm] [AMDGPU] change order of fp and sp in kernel prologue and related tests to make downstream merging easier (PR #90626)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm approved this pull request.

Description should be shortened, don't need to elaborate that this had implied test updates 

https://github.com/llvm/llvm-project/pull/90626