V4L/DVB: ngene: Added module parameter "one_adapter"

If parameter "one_adapter" is set, only one adapter per device will be attached.
Otherwise an adapter for every frontend will be attached.

Signed-off-by: Matthias Benesch <twoof7@freenet.de>
Signed-off-by: Oliver Endriss <o.endriss@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>