media: media-entity: Clarify media_entity_cleanup() usage

Being able to call cleanup functions on objects that haven't been
initialized but whose memory has been zeroed simplifies error handling.
The media_entity_cleanup() function documentation doesn't tell whether
this is allowed or not, and inspection of its implementation doesn't
provide any clue as the function is currently empty. Update the
documentation to explicitly allow this usage pattern.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>

include/media/media-entity.h

@@ -654,6 +654,10 @@ int media_entity_pads_init(struct media_entity *entity, u16 num_pads,
  *
  * This function must be called during the cleanup phase after unregistering
  * the entity (currently, it does nothing).
+ *
+ * Calling media_entity_cleanup() on a media_entity whose memory has been
+ * zeroed but that has not been initialized with media_entity_pad_init() is
+ * valid and is a no-op.
  */
 #if IS_ENABLED(CONFIG_MEDIA_CONTROLLER)
 static inline void media_entity_cleanup(struct media_entity *entity) {}