[llvm] improve debug messages in delinearization and dependence analysis (PR #156339)

[Ryotaro Kasuga via llvm-commits]

https://github.com/kasuga-fj commented:

Can you submit the changes to delinearization and DA as separate PRs?

I’ll just leave comments on what I noticed at a glance.

https://github.com/llvm/llvm-project/pull/156339