[media] ov772x: Compute window size registers at runtime

Instead of hardcoding register arrays, compute the values at runtime.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
[g.liakhovetski@gmx.de: keep (Q)VGA_* macros for now]
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>