qlcnic: fix diag resource allocation

netif_device_attach missing from error path in qlcnic_diag_alloc_res

Signed-off-by: Sony Chacko <sony.chacko@qlogic.com>
Signed-off-by: Amit Kumar Salecha <amit.salecha@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>