[media] v4l: vsp1: Add VSP+DU support

Implement internal control of the VSP pipeline to be used by the DU
DRM/KMS driver when using the VSP as an internal composer handled
through DRM/KMS only.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>