vti4: Don't count header length twice.

We currently count the size of LL_MAX_HEADER and struct iphdr
twice for vti4 devices, this leads to a wrong device mtu.
The size of LL_MAX_HEADER and struct iphdr is already counted in
ip_tunnel_bind_dev(), so don't do it again in vti_tunnel_init().

Fixes: b9959fd ("vti: switch to new ip tunnel code")
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

net/ipv4/ip_vti.c

@@ -349,7 +349,6 @@ static int vti_tunnel_init(struct net_device *dev)
 	memcpy(dev->broadcast, &iph->daddr, 4);
 
 	dev->type		= ARPHRD_TUNNEL;
-	dev->hard_header_len	= LL_MAX_HEADER + sizeof(struct iphdr);
 	dev->mtu		= ETH_DATA_LEN;
 	dev->flags		= IFF_NOARP;
 	dev->iflink		= 0;