[C++] Use 'nullptr'.

llvm-svn: 207394
diff --git a/llvm/lib/Target/ARM/ARMHazardRecognizer.h b/llvm/lib/Target/ARM/ARMHazardRecognizer.h
index e88cd0d..a8198e2 100644
--- a/llvm/lib/Target/ARM/ARMHazardRecognizer.h
+++ b/llvm/lib/Target/ARM/ARMHazardRecognizer.h
@@ -35,7 +35,7 @@
   ARMHazardRecognizer(const InstrItineraryData *ItinData,
                       const ScheduleDAG *DAG)
     : ScoreboardHazardRecognizer(ItinData, DAG, "post-RA-sched"),
-      LastMI(0) {}
+      LastMI(nullptr) {}
 
   HazardType getHazardType(SUnit *SU, int Stalls) override;
   void Reset() override;