[media] dvb-bt8xx: Don't return -EFAULT when a device is not found

When a device (or their PCI structs) are not found, the error should
be -ENODEV. -EFAULT is reserved for errors while copying arguments
from/to userspace.

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