net sched actions: add new tc_action_ops callback

Add a new callback in tc_action_ops, it will be needed by the tc actions
to compute its size when a ADD/DELETE notification message is constructed.
This routine has to take into account optional/variable size TLVs specific
per action.
Signed-off-by: Roman Mashak <mrv@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/act_api.h

@@ -97,6 +97,7 @@ struct tc_action_ops {
 			const struct tc_action_ops *,
 			struct netlink_ext_ack *);
 	void	(*stats_update)(struct tc_action *, u64, u32, u64);
+	size_t  (*get_fill_size)(const struct tc_action *act);
 	struct net_device *(*get_dev)(const struct tc_action *a);
 };