V4L/DVB (8895): pvrusb2: Fail gracefully if an alien USB ID is used

The driver includes an internal table specifying additional
information on a per device-type basis.  This works great until
somebody tries to run-time associate another USB ID with the driver.
This change should hopefully allow the driver to fail gracefully under
such a circumstance.

Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>