[llvm] [DebugInfo][Reassociate] Fix missing debug location drop (PR #95355)

[Orlando Cazalet-Hyams via llvm-commits]

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

LGTM - without this change the debug info makes it appear as if the loop body is unconditionally executed (or at least as though it's always stepped into once), dropping the location is definitely the right thing to do.

https://github.com/llvm/llvm-project/pull/95355