[llvm] [InstCombine] Simplify the pattern `a ne/eq (zext/sext (a ne/eq c))` (PR #65852)

[Nikita Popov via llvm-commits]

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

Basically LGTM, but I think this is still missing negative tests for non-equality pred1/pred2?

https://github.com/llvm/llvm-project/pull/65852