media: staging: media: imx: imx7-media-csi: Drop usage of shared helpers

None of the shared helpers are used anymore. Make this official by
dropping inclusion of imx-media.h.

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>