[media] soc-camera: Add plane layout information to struct soc_mbus_pixelfmt

To compute the value of the v4l2_pix_format::bytesperline field, we need
information about planes layout for planar formats. The new enum
soc_mbus_layout conveys that information.

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