[llvm] [NVPTX] Fix NVPTXLowerUnreachable::isLoweredToTrap logic (PR #109730)

[Justin Fargnoli via llvm-commits]

justinfargnoli wrote:

> this pass ... would generate traps even if the instruction directly before the UnreachableInst was llvm.trap()

Why is this a problem? 

https://github.com/llvm/llvm-project/pull/109730