[media] media: omap3isp: hist: Move histogram DMA to DMA engine

Replace the custom OMAP DMA API usage by DMA engine. Feature-wise the
driver has lost the ability to get notified of DMA transfers failure
through the completion handler, as the DMA engine API doesn't expose
that status information.

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