rtnetlink: Remove passing of attributes into rtnl_doit functions

With decnet converted, we can finally get rid of rta_buf and its
computations around it. It also gets rid of the minimal header
length verification since all message handlers do that explicitly
anyway.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/bridge/br_mdb.c b/net/bridge/br_mdb.c
index ee79f3f..19942e3 100644
--- a/net/bridge/br_mdb.c
+++ b/net/bridge/br_mdb.c
@@ -382,7 +382,7 @@
 	return ret;
 }
 
-static int br_mdb_add(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
+static int br_mdb_add(struct sk_buff *skb, struct nlmsghdr *nlh)
 {
 	struct net *net = sock_net(skb->sk);
 	struct br_mdb_entry *entry;
@@ -458,7 +458,7 @@
 	return err;
 }
 
-static int br_mdb_del(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
+static int br_mdb_del(struct sk_buff *skb, struct nlmsghdr *nlh)
 {
 	struct net_device *dev;
 	struct br_mdb_entry *entry;