[llvm] [AMDGPU] Skip register uses in AMDGPUResourceUsageAnalysis (PR #133242)

[Sebastian Neubauer via llvm-commits]

Flakebi wrote:

> So I would ask again, do we actually _need_ to report that one VGPR is used in Sebastian's carefully crafted compute test?

Not a definitive answer, but I think it would be cleaner to report v0 as used.
1. It allows to display the correct count in tools
2. and in case the hw behavior to always allocate at least one VGPR block changes, it still works correctly.

https://github.com/llvm/llvm-project/pull/133242