ipv4: split inet_ehashfn to hash functions per compilation unit

This duplicates a bit of code but let's us easily introduce
separate secret keys later. The separate compilation units are
ipv4/inet_hashtabbles.o, ipv4/udp.o and rds/connection.o.

Cc: Eric Dumazet <edumazet@google.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/rds/connection.c

@@ -52,9 +52,9 @@ static struct kmem_cache *rds_conn_slab;
 static struct hlist_head *rds_conn_bucket(__be32 laddr, __be32 faddr)
 {
 	/* Pass NULL, don't need struct net for hash */
-	unsigned long hash = inet_ehashfn(NULL,
-					  be32_to_cpu(laddr), 0,
-					  be32_to_cpu(faddr), 0);
+	unsigned long hash = __inet_ehashfn(be32_to_cpu(laddr), 0,
+					    be32_to_cpu(faddr), 0,
+					    inet_ehash_secret);
 	return &rds_conn_hash[hash & RDS_CONNECTION_HASH_MASK];
 }