Convert a bunch of loops to foreach.  NFC.

After r244074, we now have a successors() method to iterate over
all the successors of a TerminatorInst.  This commit changes a bunch
of eligible loops to use it.

llvm-svn: 244260
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 8a0bd60..874604d 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -2565,8 +2565,7 @@
   BasicBlock *KeepEdge2 = TrueBB != FalseBB ? FalseBB : nullptr;
 
   // Then remove the rest.
-  for (unsigned I = 0, E = OldTerm->getNumSuccessors(); I != E; ++I) {
-    BasicBlock *Succ = OldTerm->getSuccessor(I);
+  for (BasicBlock *Succ : OldTerm->successors()) {
     // Make sure only to keep exactly one copy of each edge.
     if (Succ == KeepEdge1)
       KeepEdge1 = nullptr;