mpci: Use the first scheduler for MPCI

Avoid use of processor index 0 which may have no scheduler assigned.

cpukit/score/src/mpci.c

@@ -152,7 +152,7 @@ static void _MPCI_Create_server( void )
   _Thread_Initialize(
     &_Thread_Internal_information,
     _MPCI_Receive_server_tcb,
-    _Scheduler_Get_by_CPU_index( _SMP_Get_current_processor() ),
+    &_Scheduler_Table[ 0 ],
     NULL,        /* allocate the stack */
     _Stack_Minimum() +
       CPU_MPCI_RECEIVE_SERVER_EXTRA_STACK +

cpukit/score/src/threadmp.c

@@ -77,7 +77,7 @@ void _Thread_MP_Handler_initialization (
 
     proxy->Scheduler.nodes = &proxy->Scheduler_node;
     _Scheduler_Node_do_initialize(
-      _Scheduler_Get_by_CPU_index( 0 ),
+      &_Scheduler_Table[ 0 ],
       &proxy->Scheduler_node,
       (Thread_Control *) proxy,
       0