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/can/gw.c b/net/can/gw.c
index 2d117dc..2dc619d 100644
--- a/net/can/gw.c
+++ b/net/can/gw.c
@@ -778,8 +778,7 @@
 	return 0;
 }
 
-static int cgw_create_job(struct sk_buff *skb,  struct nlmsghdr *nlh,
-			  void *arg)
+static int cgw_create_job(struct sk_buff *skb,  struct nlmsghdr *nlh)
 {
 	struct rtcanmsg *r;
 	struct cgw_job *gwj;
@@ -868,7 +867,7 @@
 	}
 }
 
-static int cgw_remove_job(struct sk_buff *skb,  struct nlmsghdr *nlh, void *arg)
+static int cgw_remove_job(struct sk_buff *skb,  struct nlmsghdr *nlh)
 {
 	struct cgw_job *gwj = NULL;
 	struct hlist_node *nx;