batman-adv: add reference counting for type batadv_tt_orig_list_entry

The batadv_tt_orig_list_entry structure didn't have any refcounting mechanism so
far. This patch introduces it and makes the structure being usable in much more
complex context.

Signed-off-by: Antonio Quartulli <ordex@autistici.org>
diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index 7812b6e..664ef81 100644
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -282,6 +282,7 @@
 struct batadv_tt_orig_list_entry {
 	struct batadv_orig_node *orig_node;
 	uint8_t ttvn;
+	atomic_t refcount;
 	struct rcu_head rcu;
 	struct hlist_node list;
 };