[clang] [llvm] [AMDGPU] Move AMDGPUAttributor earlier with lowering kernel attributes (PR #177432)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

Moving the pass and merging the passes are also two separate tasks, should not be in same PR 

https://github.com/llvm/llvm-project/pull/177432