[media] v4l: vsp1: Use display lists with the userspace API

Don't restrict display list usage to the DRM pipeline, use them
unconditionally. This prepares the driver to support the request API.

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