As we develop the partition algorithm, we need to store more information
per partition to describe the phase and other parameters.

To keep this data together, further abstract the existing v4l2_rect
into a partition specific structure. As partitions only have horizontal
coordinates, store the left and width values only.

When generating the partition windows, operate directly on the partition
struct rather than copying and duplicating the processed data
Signed-off-by: NKieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NHans Verkuil <hansverk@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>