media: staging: media: imx: imx7-media-csi: Drop the imx_media notifier

The V4L2 async notifier embedded in the imx_media_dev structure is
triggered when the CSI bridge subdev is registered. We don't need an
async notifier for this, as we can call the .complete() handler directly
from the CSI bridge subdev .registered() handler.

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>