netlink: add netlink_dump_control structure for netlink_dump_start()

Davem considers that the argument list of this interface is getting
out of control. This patch tries to address this issue following
his proposal:

struct netlink_dump_control c = { .dump = dump, .done = done, ... };

netlink_dump_start(..., &c);

Suggested by David S. Miller.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index a115471..9f40441 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -563,8 +563,13 @@
 			return -EOPNOTSUPP;
 
 		genl_unlock();
-		err = netlink_dump_start(net->genl_sock, skb, nlh,
-					 ops->dumpit, ops->done, 0);
+		{
+			struct netlink_dump_control c = {
+				.dump = ops->dumpit,
+				.done = ops->done,
+			};
+			err = netlink_dump_start(net->genl_sock, skb, nlh, &c);
+		}
 		genl_lock();
 		return err;
 	}