batman-adv: split tvlv into a separate file

The tvlv functionality in main.c is mostly unrelated to the rest of the
content. It still takes up a large portion of this source file (~45%, 588
lines). Moving it to a separate file makes it better visible as a main
component of the batman-adv implementation and hides it less in the other
helper functions in main.c

Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
[sven@narfation.org: fix conflicts with current version, fix includes,
rewrote commit message]
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/multicast.c b/net/batman-adv/multicast.c
index d3222db..0e7d78f 100644
--- a/net/batman-adv/multicast.c
+++ b/net/batman-adv/multicast.c
@@ -57,6 +57,7 @@
 #include "hash.h"
 #include "packet.h"
 #include "translation-table.h"
+#include "tvlv.h"
 
 /**
  * batadv_mcast_get_bridge - get the bridge on top of the softif if it exists