media: cobalt: do not register subdev nodes

media: cobalt: do not register subdev nodes

In the distant past the adv7604 driver used private controls. In order
to access them the v4l-subdevX nodes were needed. Later the is_private
tag was removed in the adv7604 driver and the need for v4l-subdevX
device nodes disappeared.

Remove the creation of those device nodes from this driver.

Note: the cobalt card is only used inside Cisco and we never actually
used the v4l-subdevX nodes for anything. So this API change can be done
safely without breaking anything.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>