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/phonet/pn_netlink.c b/net/phonet/pn_netlink.c
index 0193630..dc15f43 100644
--- a/net/phonet/pn_netlink.c
+++ b/net/phonet/pn_netlink.c
@@ -61,7 +61,7 @@
 	[IFA_LOCAL] = { .type = NLA_U8 },
 };
 
-static int addr_doit(struct sk_buff *skb, struct nlmsghdr *nlh, void *attr)
+static int addr_doit(struct sk_buff *skb, struct nlmsghdr *nlh)
 {
 	struct net *net = sock_net(skb->sk);
 	struct nlattr *tb[IFA_MAX+1];
@@ -224,7 +224,7 @@
 	[RTA_OIF] = { .type = NLA_U32 },
 };
 
-static int route_doit(struct sk_buff *skb, struct nlmsghdr *nlh, void *attr)
+static int route_doit(struct sk_buff *skb, struct nlmsghdr *nlh)
 {
 	struct net *net = sock_net(skb->sk);
 	struct nlattr *tb[RTA_MAX+1];