bsps/irq: Fix type limits warnings

Set BSP_INTERRUPT_VECTOR_COUNT to 1 to avoid type limits and array
bounds warnings.

Make sure all functions using the default interrupt controller
implementation return a status of RTEMS_UNSATISFIED.

Update #5298.
Close #5377.

bsps/shared/irq/irq-default.c

@@ -45,7 +45,7 @@ rtems_status_code bsp_interrupt_get_attributes(
   (void) vector;
   (void) attributes;
 
-  return RTEMS_SUCCESSFUL;
+  return RTEMS_UNSATISFIED;
 }
 
 rtems_status_code bsp_interrupt_is_pending(