media: dt-bindings: media: sun6i-a31-csi: Add internal output port to the ISP

Some Allwinner devices come with an Image Signal Processor (ISP) that
allows processing camera data to produce good-looking images,
especially from raw bayer representations.

The ISP does not have a dedicated capture path: it is fed directly by
one of the CSI controllers, which can be selected at run-time.

Represent this possibility as a graph connection between the CSI
controller and the ISP in the device-tree bindings.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>