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/include/net/neighbour.h b/include/net/neighbour.h
index bc66bab..9f912e4 100644
--- a/include/net/neighbour.h
+++ b/include/net/neighbour.h
@@ -193,6 +193,7 @@
 	int			family;
 	int			entry_size;
 	int			key_len;
+	__be16			protocol;
 	__u32			(*hash)(const void *pkey,
 					const struct net_device *dev,
 					__u32 *hash_rnd);