[clang] [llvm] [AMDGPU] Add per-kernel kernarg preload count (PR #211059)

[Aaron Ballman via cfe-commits]

https://github.com/AaronBallman commented:

The attribute bits LGTM but this should not land until @arsenm is happy with the design, so I'm holding off on accepting until that is settled.

https://github.com/llvm/llvm-project/pull/211059