media: v4l2: mem2mem: Fix typos in v4l2_m2m_dev documentation

The v4l2_m2m_dev structure documentation incorrectly references the
v4l2_m2m_unregister_media_controller() function when it actually means
v4l2_m2m_register_media_controller(). Fix it.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/v4l2-core/v4l2-mem2mem.c

@@ -68,16 +68,16 @@ static const char * const m2m_entity_name[] = {
  * struct v4l2_m2m_dev - per-device context
  * @source:		&struct media_entity pointer with the source entity
  *			Used only when the M2M device is registered via
- *			v4l2_m2m_unregister_media_controller().
+ *			v4l2_m2m_register_media_controller().
  * @source_pad:		&struct media_pad with the source pad.
  *			Used only when the M2M device is registered via
- *			v4l2_m2m_unregister_media_controller().
+ *			v4l2_m2m_register_media_controller().
  * @sink:		&struct media_entity pointer with the sink entity
  *			Used only when the M2M device is registered via
- *			v4l2_m2m_unregister_media_controller().
+ *			v4l2_m2m_register_media_controller().
  * @sink_pad:		&struct media_pad with the sink pad.
  *			Used only when the M2M device is registered via
- *			v4l2_m2m_unregister_media_controller().
+ *			v4l2_m2m_register_media_controller().
  * @proc:		&struct media_entity pointer with the M2M device itself.
  * @proc_pads:		&struct media_pad with the @proc pads.
  *			Used only when the M2M device is registered via