[BRIDGE]: handle out-of-ports corner case.

net/bridge/br_if.c

@@ -155,8 +155,6 @@ static struct net_bridge_port *new_nbp(struct net_bridge *br, struct net_device
 	p->path_cost = br_initial_port_cost(dev);
 	p->priority = 0x80;
 
-	dev->br_port = p;
-
 	for (i=1;i<255;i++)
 		if (br_get_port(br, i) == NULL)
 			break;
@@ -166,6 +164,8 @@ static struct net_bridge_port *new_nbp(struct net_bridge *br, struct net_device
 		return NULL;
 	}
 
+	dev->br_port = p;
+
 	p->port_no = i;
 	br_init_port(p);
 	p->state = BR_STATE_DISABLED;