media: v4l: vsp1: Calculate partition sizes at stream start

Previously the active window and partition sizes for each partition were
calculated for each partition every frame. This data is constant and
only needs to be calculated once at the start of the stream.

Extend the vsp1_pipe object to dynamically store the number of partitions
required and pre-calculate the partition sizes into this table.

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>