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

[weiwei chen via llvm-commits]

weiweichen wrote:

Got distracted by some other things and getting back to this now. If there is no objections, I'm gonna merge this one, and will definitely do follow-up PRs if there are more issues need to be addressed. 🙏 

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