[llvm] [llvm][NVPTX] Fix quadratic runtime in ProxyRegErasure (PR #105730)

[Jeff Niu via llvm-commits]

Mogball wrote:

NVPTX backend compile times are top-of-mind for me right now. So if there are any problems, you'll definitely hear about them from me! 

https://github.com/llvm/llvm-project/pull/105730