score: Optimize EDF SMP scheduler ops

The schedule operation is only called by rtems_task_mode().  It is
called if preempt mode of the executing thread changes from disabled to
enabled.  Since the EDF SMP scheduler does not support the disabled
preemption mode, the schedule operation is never called.

cpukit/include/rtems/score/scheduleredfsmp.h

@@ -110,7 +110,7 @@ typedef struct {
 #define SCHEDULER_EDF_SMP_ENTRY_POINTS \
   { \
     _Scheduler_EDF_SMP_Initialize, \
-    _Scheduler_default_Schedule, \
+    NULL, \
     _Scheduler_EDF_SMP_Yield, \
     _Scheduler_EDF_SMP_Block, \
     _Scheduler_EDF_SMP_Unblock, \