Define a frame sync event to tell user space when the reception of a frame
starts.
Signed-off-by: NSakari Ailus <sakari.ailus@iki.fi>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>