batman-adv: Consolidate logging related functions

There are several places in batman-adv which provide logging related
functions. These should be grouped together in the log.* files to make them
easier to find.

Reported-by: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c
index a3483f6..ad2c37c 100644
--- a/net/batman-adv/hard-interface.c
+++ b/net/batman-adv/hard-interface.c
@@ -42,6 +42,7 @@
 #include "debugfs.h"
 #include "distributed-arp-table.h"
 #include "gateway_client.h"
+#include "log.h"
 #include "originator.h"
 #include "packet.h"
 #include "send.h"