event: The device setter work on sub-types

Instead of just setting the input device pointer in the private event
data, it should also set the field in the event sub-types, so that
direct access to the structures still works.

clutter/clutter-event.c

@@ -550,8 +550,6 @@ clutter_event_set_device (ClutterEvent       *event,
       ClutterEventPrivate *real_event = (ClutterEventPrivate *) event;
 
       real_event->device = device;
-
-      return;
     }
 
   switch (event->type)