[llvm] [OpenMPOpt] Fix incorrect end-of-kernel barrier removal (PR #65670)

[Johannes Doerfert via llvm-commits]

https://github.com/jdoerfert commented:

I need to look at it in more detail, but the reasoning makes sense (as already tried to fix in https://github.com/llvm/llvm-project/commit/24656e995ae9c5893fa32db62863e55c3c70c5e2).

https://github.com/llvm/llvm-project/pull/65670