media: mc-entity: Rename media_entity_remote_pad() to media_pad_remote_pad_first()

The media_entity_remote_pad() is misnamed, as it operates on a pad and
not an entity. Rename it to media_pad_remote_pad_first() to clarify its
behaviour.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>