media: v4l: vsp1: Allow entities to participate in the partition algorithm

The configuration of the pipeline and entities directly affects the
inputs required to each entity for the partition algorithm. Thus it
makes sense to involve those entities in the decision making process.

Extend the entity ops API to provide an optional .partition() operation.
This allows entities that affect the partition window to adapt the
window based on their configuration.

Entities implementing this operation must update the window parameter in
place, which will then be passed up the pipeline. This creates a process
whereby each entity describes what is required to satisfy the required
output to its predecessor in the pipeline.

Signed-off-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hansverk@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>