[clang] [CIR] Fix building ClangIR after RegionBranchOpInterface revamp (PR #165441)

[Mehdi Amini via cfe-commits]

================
@@ -26,14 +26,16 @@ void LoopOpInterface::getLoopOpSuccessorRegions(
   }
 
----------------
joker-eph wrote:

```suggestion
  Region *parentRegion = point.getTerminatorPredecessorOrNull()->getParentRegion();
```



https://github.com/llvm/llvm-project/pull/165441