media: v4l: Set line based metadata flag in V4L2 core

Set (and unset) the V4L2_FMT_FLAG_META_LINE_BASED flag in struct
v4l2_fmtdesc based on the format after returning the driver callback for
enumerating formats. This way the drivers don't need to care about the
flag.

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