[media] omap3isp: queue: Use sg_table structure

Replace the sglen and sglist fields stored in the buffer structure with
an sg_table. This allows using the sg table allocation helper function.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>