[ScheduleDAGMILive] Fix typo in comment.

Differential Revision: https://reviews.llvm.org/D67478

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@371916 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/MachineScheduler.cpp

@@ -985,7 +985,7 @@ void ScheduleDAGMILive::enterRegion(MachineBasicBlock *bb,
          "ShouldTrackLaneMasks requires ShouldTrackPressure");
 }
 
-// Setup the register pressure trackers for the top scheduled top and bottom
+// Setup the register pressure trackers for the top scheduled and bottom
 // scheduled regions.
 void ScheduleDAGMILive::initRegPressure() {
   VRegUses.clear();