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

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.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D130425

Author: slydiman

llvm/lib/CodeGen/MachineScheduler.cpp

@@ -750,7 +750,7 @@ void ScheduleDAGMI::moveInstruction(
 }
 
 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;