IB/usnic: Fix resource leak in error case

Signed-off-by: Dave Goodell <dgoodell@cisco.com>
Reviewed-by: Reese Faucette <rfaucett@cisco.com>
Reviewed-by: Xuyang Wang <xuywang@cisco.com>
Signed-off-by: Nelson Escobar <neescoba@cisco.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>