IB/usnic: Fix error return code

If 'pci_register_driver' fails, we return 'err' which is known to be 0.
Return the error instead.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Doug Ledford <dledford@redhat.com>
1 file changed