media: imx: add csc/scaler mem2mem device

Add a single imx-media mem2mem video device that uses the IPU IC PP
(image converter post processing) task for scaling and colorspace
conversion.
On i.MX6Q/DL SoCs with two IPUs currently only the first IPU is used.

The hardware only supports writing to destination buffers up to
1024x1024 pixels in a single pass, arbitrary sizes can be achieved
by rendering multiple tiles per frame.

[slongerbeam@gmail.com: use ipu_image_convert_adjust(), fix
 device_run() error handling, add missing media-device header,
 unregister and remove the mem2mem device in error paths in
 imx_media_probe_complete() and in imx_media_remove(), updated
 for sync subdev registration]

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Steve Longerbeam <slongerbeam@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
[hverkuil-cisco@xs4all.nl: correct two minor checkpatch issues]
[hverkuil-cisco@xs4all.nl: sparse warning: make imx6_media_probe_complete static]
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>