Revert "ARM: Enable MachineScheduler and disable PostRAScheduler for swift."

This reverts commit r242500.

It broke some internal tests and Matthias asked me to revert it while he
is investigating.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242553 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/MC/MCSchedule.h

@@ -206,9 +206,6 @@ struct MCSchedModel {
   /// scheduling class (itinerary class or SchedRW list).
   bool isComplete() const { return CompleteModel; }
 
-  /// Return true if machine supports out of order execution.
-  bool isOutOfOrder() const { return MicroOpBufferSize > 1; }
-
   unsigned getNumProcResourceKinds() const {
     return NumProcResourceKinds;
   }