Remove unused PrepareReschedule function

src/core/arm/arm_interface.h

@@ -174,9 +174,6 @@ public:
     /// Clears the exclusive monitor's state.
     virtual void ClearExclusiveState() = 0;
 
-    /// Prepare core for thread reschedule (if needed to correctly handle state)
-    virtual void PrepareReschedule() = 0;
-
     /// Signal an interrupt and ask the core to halt as soon as possible.
     virtual void SignalInterrupt() = 0;