batman-adv: Prefix main defines with BATADV_

Reported-by: Martin Hundebøll <martin@hundeboll.net>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c
index 9b1cb23..e7eba9c 100644
--- a/net/batman-adv/hard-interface.c
+++ b/net/batman-adv/hard-interface.c
@@ -548,7 +548,7 @@
 	struct net_device *net_device = NULL;
 	bool ret = false;
 
-	if (ifindex == NULL_IFINDEX)
+	if (ifindex == BATADV_NULL_IFINDEX)
 		goto out;
 
 	net_device = dev_get_by_index(&init_net, ifindex);