[media] dt3155v4l: add v4l2_device support

Add struct v4l2_device and register it. Also move the request_irq to
probe instead of doing that in open().

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>