[llvm] [AMDGPU] Fix hidden kernarg preload count inconsistency (PR #116759)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

> It is possible that the number of hidden arguments that are selected to be preloaded in AMDGPULowerKernel arguments and isel can differ.

This should not happen. The introduction of arguments to preload should be precise 

https://github.com/llvm/llvm-project/pull/116759