[media] media: atmel-isi: add primary DT support

This patch add the DT support for Atmel ISI driver.
It use the same v4l2 DT interface that defined in video-interfaces.txt.

Signed-off-by: Josh Wu <josh.wu@atmel.com>
Cc: devicetree@vger.kernel.org
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>