[llvm] [NVPTX] Check Before inserting AddrSpaceCastInst in NVPTXLoweringAlloca (PR #106127)

[Justin Fargnoli via llvm-commits]

justinfargnoli wrote:

> Good point! Thank you for checking the spec! Leaving the check as is and perhaps the fix in this PR makes more sense?

Agreed :) 

https://github.com/llvm/llvm-project/pull/106127