net: remove MTU limits on a few ether_setup callers

These few drivers call ether_setup(), but have no ndo_change_mtu, and thus
were overlooked for changes to MTU range checking behavior. They
previously had no range checks, so for feature-parity, set their min_mtu
to 0 and max_mtu to ETH_MAX_MTU (65535), instead of the 68 and 1500
inherited from the ether_setup() changes. Fine-tuning can come after we get
back to full feature-parity here.

CC: netdev@vger.kernel.org
Reported-by: Asbjoern Sloth Toennesen <asbjorn@asbjorn.st>
CC: Asbjoern Sloth Toennesen <asbjorn@asbjorn.st>
CC: R Parameswaran <parameswaran.r7@gmail.com>
Signed-off-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/l2tp/l2tp_eth.c

@@ -259,6 +259,8 @@ static int l2tp_eth_create(struct net *net, u32 tunnel_id, u32 session_id, u32 p
 		session->mtu = dev->mtu - session->hdr_len;
 	dev->mtu = session->mtu;
 	dev->needed_headroom += session->hdr_len;
+	dev->min_mtu = 0;
+	dev->max_mtu = ETH_MAX_MTU;
 
 	priv = netdev_priv(dev);
 	priv->dev = dev;