net: sched: extend proto ops with 'put' callback

Add optional tp->ops->put() API to be implemented for filter reference
counting. This new function is called by cls API to release filter
reference for filters returned by tp->ops->change() or tp->ops->get()
functions. Implement tfilter_put() helper to call tp->ops->put() only for
classifiers that implement it.

Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index e8cf36e..410dda8 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -277,6 +277,7 @@ struct tcf_proto_ops {
 					   struct netlink_ext_ack *extack);
 
 	void*			(*get)(struct tcf_proto*, u32 handle);
+	void			(*put)(struct tcf_proto *tp, void *f);
 	int			(*change)(struct net *net, struct sk_buff *,
 					struct tcf_proto*, unsigned long,
 					u32 handle, struct nlattr **,