[llvm] [LoopInterchange] Prevent from undoing its own transformation (PR #127473)

[Michael Kruse via llvm-commits]

https://github.com/Meinersbur requested changes to this pull request.

> Could you please move the refactorings/cleanups out of this patch?

Please still consider.

https://github.com/llvm/llvm-project/pull/127473