media: rcar-vin: unregister video device on driver removal

media: rcar-vin: unregister video device on driver removal

If the video device was registered by the complete() callback it should
be unregistered when a device is unbound from the driver. Protect from
printing an uninitialized video device node name by adding a check in
rvin_v4l2_unregister() to identify that the video device is registered.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>