media: renesas: vsp1: Move partition calculation to vsp1_pipe.c

The partition calculation code, located in vsp1_video.c, is not specific
to video pipelines. To prepare for its usage in DRM pipelines, move it
to vsp1_pipe.c.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi+renesas@ideasonboard.com>