[clang] [llvm] [NVPTX] Fix for device function pointer having the same name as generated callprototype (PR #205639)

[Daniel Donenfeld via cfe-commits]

daniel-donenfeld wrote:

I think the new pass was overly complex, I moved the logic to NVPTXAsmPrinter which resolves the issues with needing to register all the global symbols. It special cases the callprototype logic when lowering the MachineOperands but its wrapped in helpers to make it more clear.

@justinfargnoli Can you take another look? 

https://github.com/llvm/llvm-project/pull/205639