batman-adv: Drop usage of export.h

The linux/export.h include was introduced in commit 9bcb94c8
("batman-adv: Introduce missing headers for genetlink restructure") to have
access to THIS_MODULE. But with commit 5b20755b ("init: move
THIS_MODULE from <linux/export.h> to <linux/init.h>"), it was moved and the
include for export.h is no longer needed.
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>

net/batman-adv/netlink.c

@@ -15,7 +15,6 @@
 #include <linux/cache.h>
 #include <linux/err.h>
 #include <linux/errno.h>
-#include <linux/export.h>
 #include <linux/genetlink.h>
 #include <linux/gfp.h>
 #include <linux/if_ether.h>