[llvm] [AMDGPU][Scheduler] Fix non-monotonic SlotIndex after schedule revert (PR #192039)

[via llvm-commits]

================
@@ -369,6 +369,9 @@ class GCNSchedStage {
   // RP after scheduling the current region.
   GCNRegPressure PressureAfter;
 
+  // Whether checkScheduling reverted the schedule for the current region.
+  bool ScheduleReverted = false;
----------------
michaelselehov wrote:

Done. Same as above.

https://github.com/llvm/llvm-project/pull/192039