media: v4l: vsp1: Remove redundant context variables

The vsp1_pipe object context variables for div_size and
current_partition allowed state to be maintained through processing the
partitions during processing.

Now that the partition tables are calculated during stream on, there is
no requirement to store these variables in the pipe object.

Utilise local variables for the processing as required.

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>