[llvm] [CodeGen][PM] Use errs() instead of dbgs() in printer passes (PR #118469)

[via llvm-commits]

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

In fact I see `llvm::errs()` is also unbuffered:
https://github.com/llvm/llvm-project/blob/81d82cac8c4cbd006bf991fd7380de2d72858d1c/llvm/lib/Support/raw_ostream.cpp#L910-L915
But +1 for this, because `dbg()` should be used in debug context and is no different with `errs()` in release build.

https://github.com/llvm/llvm-project/pull/118469