[CodeGen] Fixed undeclared MISchedCutoff in case of NDEBUG and LLVM_ENABLE_ABI_BREAKING_CHECKS

[slydiman]

Summary

This patch fixes the error llvm/lib/CodeGen/MachineScheduler.cpp(755): error C2065: 'MISchedCutoff': undeclared identifier in case of NDEBUG and LLVM_ENABLE_ABI_BREAKING_CHECKS.
Note MISchedCutoff is declared under #ifndef NDEBUG.

[RKSimon]

LGTM

llvm/lib/CodeGen/MachineScheduler.cpp

if (LIS)
     LIS->handleMove(*MI, /*UpdateFlags=*/true);
 
   // Recede RegionBegin if an instruction moves above the first.
   if (RegionBegin == InsertPos)
     RegionBegin = MI;
 }
 
 bool ScheduleDAGMI::checkSchedLimit() {
-#if LLVM_ENABLE_ABI_BREAKING_CHECKS
+#if LLVM_ENABLE_ABI_BREAKING_CHECKS && !defined(NDEBUG)
   if (NumInstrsScheduled == MISchedCutoff && MISchedCutoff != ~0U) {
     CurrentTop = CurrentBottom;
     return false;
   }
   ++NumInstrsScheduled;
 #endif
   return true;
 }