l2tp: remove useless device duplication test in l2tp_eth_create()

There's no need to verify that cfg->ifname is unique at this point.
register_netdev() will return -EEXIST if asked to create a device with
a name that's alrealy in use.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/l2tp/l2tp_eth.c

@@ -280,12 +280,6 @@ static int l2tp_eth_create(struct net *net, u32 tunnel_id, u32 session_id, u32 p
 	}
 
 	if (cfg->ifname) {
-		dev = dev_get_by_name(net, cfg->ifname);
-		if (dev) {
-			dev_put(dev);
-			rc = -EEXIST;
-			goto out;
-		}
 		strlcpy(name, cfg->ifname, IFNAMSIZ);
 		name_assign_type = NET_NAME_USER;
 	} else {