lpfc: Fix crash when unregistering default rpi.

The default rpi completion handler does back to back puts to force the
removal of the ndlp. This ends up calling lpfc_unreg_rpi after the
reference count is at 0.

Fix:  Check the reference count of the ndlp before getting the ref to
make sure we are not getting a reference on a removed object.
Signed-off-by: Dick Kennedy <dick.kennedy@avagotech.com>
Signed-off-by: James Smart <james.smart@avagotech.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/lpfc/lpfc_hbadisc.c

@@ -4545,7 +4545,8 @@ lpfc_unreg_rpi(struct lpfc_vport *vport, struct lpfc_nodelist *ndlp)
 				    (!(vport->load_flag & FC_UNLOADING)) &&
 				    (bf_get(lpfc_sli_intf_if_type,
 				     &phba->sli4_hba.sli_intf) ==
-				      LPFC_SLI_INTF_IF_TYPE_2)) {
+				      LPFC_SLI_INTF_IF_TYPE_2) &&
+				    (atomic_read(&ndlp->kref.refcount) > 0)) {
 					mbox->context1 = lpfc_nlp_get(ndlp);
 					mbox->mbox_cmpl =
 						lpfc_sli4_unreg_rpi_cmpl_clr;