V4L/DVB: ngene: Fix unloading of module

Fixed unloading of module ngene.

Signed-off-by: Roland Praml <pram@gmx.de>
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>