scsi: qla4xxx: fix a potential NULL pointer dereference

In case iscsi_lookup_endpoint fails, the fix returns -EINVAL to avoid NULL
pointer dereference.
Signed-off-by: Kangjie Lu <kjlu@umn.edu>
Acked-by: Manish Rangankar <mrangankar@marvell.com>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/qla4xxx/ql4_os.c

@@ -3203,6 +3203,8 @@ static int qla4xxx_conn_bind(struct iscsi_cls_session *cls_session,
 	if (iscsi_conn_bind(cls_session, cls_conn, is_leading))
 		return -EINVAL;
 	ep = iscsi_lookup_endpoint(transport_fd);
+	if (!ep)
+		return -EINVAL;
 	conn = cls_conn->dd_data;
 	qla_conn = conn->dd_data;
 	qla_conn->qla_ep = ep->dd_data;