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

[Justin Fargnoli via llvm-commits]

justinfargnoli wrote:

> do an explicit cast which will actually fail assertion with `AddrSpaceCastInst`

@weiweichen, where is this assertion? Maybe it needs to be changed. 

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