openvswitch: remove BUG_ON from get_dpdev

if local is NULL pointer, and the following access of local's
dev will trigger panic, which is same as BUG_ON
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/openvswitch/vport-netdev.c

@@ -84,7 +84,6 @@ static struct net_device *get_dpdev(const struct datapath *dp)
 	struct vport *local;
 
 	local = ovs_vport_ovsl(dp, OVSP_LOCAL);
-	BUG_ON(!local);
 	return local->dev;
 }