batman-adv: Convert batadv_hard_iface 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>
diff --git a/net/batman-adv/bat_iv_ogm.c b/net/batman-adv/bat_iv_ogm.c
index affcbb5..bf0e7d6 100644
--- a/net/batman-adv/bat_iv_ogm.c
+++ b/net/batman-adv/bat_iv_ogm.c
@@ -644,10 +644,10 @@
 	unsigned char *skb_buff;
 	unsigned int skb_size;
 
-	if (!atomic_inc_not_zero(&if_incoming->refcount))
+	if (!kref_get_unless_zero(&if_incoming->refcount))
 		return;
 
-	if (!atomic_inc_not_zero(&if_outgoing->refcount))
+	if (!kref_get_unless_zero(&if_outgoing->refcount))
 		goto out_free_incoming;
 
 	/* own packet should always be scheduled */