batman-adv: Convert batadv_orig_node to kref

batman-adv uses a self-written reference implementation which is just based
on atomic_t. This is less obvious when reading the code than kref and
therefore increases the change that the reference counting will be missed.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <a@unstable.cc>

net/batman-adv/network-coding.c

@@ -858,7 +858,7 @@ static struct batadv_nc_node
 	if (!nc_node)
 		return NULL;
 
-	if (!atomic_inc_not_zero(&orig_neigh_node->refcount))
+	if (!kref_get_unless_zero(&orig_neigh_node->refcount))
 		goto free;
 
 	/* Initialize nc_node */