[media] sh-mobile-ceu-driver: support max width and height in DT

Some CEU implementations have non-standard (larger) maximum supported
width and height values. Add two OF properties to specify them.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>