mm_lock.c: reformat preprocessor format

mm/mm_heap/mm_lock.c

@@ -62,19 +62,18 @@ int mm_lock(FAR struct mm_heap_s *heap)
 
   if (up_interrupt_context())
     {
-#if !defined(CONFIG_SMP)
+#  if !defined(CONFIG_SMP)
       /* Check the mutex value, if held by someone, then return false.
        * Or, touch the heap internal data directly.
        */
 
       return nxmutex_is_locked(&heap->mm_lock) ? -EAGAIN : 0;
-#else
+#  else
       /* Can't take mutex in SMP interrupt handler */
 
       return -EAGAIN;
-#endif
+#  endif
     }
-  else
 #endif
 
   /* _SCHED_GETTID() returns the task ID of the task at the head of the