media: staging: media: imx: imx7-media-csi: Don't populate vdev lists

The imx_media_dev framework maintains a per-pad list of connected video
devices, created once all subdevs have been bound. This is used for two
purposes, updating V4L2 control inheritance when links change, and
relaying subdev events to video nodes. None of these are used by the
imx7-media-csi driver as it implements the MC-centric approach. Drop
them.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Rui Miguel Silva <rmfrfs@gmail.com>
Tested-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>