media: imx: imx7-mipi-csis: Don't use imx-media-utils helpers

The imx7-mipi-csis only uses the imx_media_init_mbus_fmt() function from
the imx-media-utils helpers. The helpers don't support all the media bus
formats used by this driver, and are thus a bad fit. As the MIPI CSIS is
a standalone IP core that could be integrated in other SoCs, let's not
use the helper.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Rui Miguel Silva <rmfrfs@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>