media: rkvdec: Add get_image_fmt ops

media: rkvdec: Add get_image_fmt ops

Add support for a get_image_fmt() ops that returns the required image
format.

The CAPTURE format is reset when the required image format changes and
the buffer queue is not busy.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Tested-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Reviewed-by: Jonas Karlman <jonas@kwiboo.se>
Co-developed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>