[media] v4l: vsp1: Determine partition requirements for scaled images

The partition algorithm needs to determine the capabilities of each
entity in the pipeline to identify the correct maximum partition width.

Extend the vsp1 entity operations to provide a max_width operation and
use this call to calculate the number of partitions that will be
processed by the algorithm.

Gen 2 hardware does not require multiple partitioning, and as such
will always return a single partition.

Signed-off-by: Kieran Bingham <kieran+renesas@bingham.xyz>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>