[LoopPeel] Make sure PeelLast is always initialized.

Make sure PeelLast is initialized on all paths.

Should fix MSan bootstrap failures
     https://lab.llvm.org/buildbot/#/builders/164/builds/9992
     https://lab.llvm.org/buildbot/#/builders/94/builds/7158

Fixup after #139551.

Author: fhahn

llvm/lib/Transforms/Utils/LoopPeel.cpp

@@ -596,6 +596,7 @@ void llvm::computePeelCount(Loop *L, unsigned LoopSize,
   // TTI.getPeelingPreferences or by the flag -unroll-peel-count.
   unsigned TargetPeelCount = PP.PeelCount;
   PP.PeelCount = 0;
+  PP.PeelLast = false;
   if (!canPeel(L))
     return;