neigh: Don't require dst in neigh_hh_init

- Add protocol to neigh_tbl so that dst->ops->protocol is not needed
- Acquire the device from neigh->dev

This results in a neigh_hh_init that will cache the samve values
regardless of the packets flowing through it.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index bca5b9d..6b8aad6a 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -152,6 +152,7 @@
 struct neigh_table arp_tbl = {
 	.family		= AF_INET,
 	.key_len	= 4,
+	.protocol	= cpu_to_be16(ETH_P_IP),
 	.hash		= arp_hash,
 	.constructor	= arp_constructor,
 	.proxy_redo	= parp_redo,