[llvm] [NVPTX] Fix code generation for `trap-unreachable`. (PR #67478)

[Christian Sigg via llvm-commits]

chsigg wrote:

> I think we would then want skip lowering ISD::TRAP, so that we don't end up with trap; exit; trap; sequences.

Actually, no. Because `ISD::TRAP` can also be generated elsewhere, not just from `unreachable` (e.g. from `Intrinsic::trap`).

https://github.com/llvm/llvm-project/pull/67478