[llvm] [LoopInterchange] Relax the legality check to accept more patterns (PR #139690)

[Michael Kruse via llvm-commits]

https://github.com/Meinersbur approved this pull request.

Using GitHub's PR workflow [is not required](https://llvm.org/docs/GitHub.html#landing-your-change). Once it is accepted, you can push your patch using
```
git merge --squash origin/main # Squash all commits into one
git commit --amend # Use the commit message from the PR summary; add "closes #118267" so GitHub can link it to the original PR

git push origin HEAD:main -n
# confirm that it would push what you want
git push origin HEAD:main
```

https://github.com/llvm/llvm-project/pull/139690