batman-adv: Revert "Drop lockdep.h include for soft-interface.c"

The commit 1a33e10e ("net: partially revert dynamic lockdep key
changes") reverts the commit ab92d68f ("net: core: add generic lockdep
keys"). But it forgot to also revert the commit 5759af06 ("batman-adv:
Drop lockdep.h include for soft-interface.c") which depends on the latter.
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>

net/batman-adv/soft-interface.c

@@ -22,6 +22,7 @@
 #include <linux/kernel.h>
 #include <linux/kref.h>
 #include <linux/list.h>
+#include <linux/lockdep.h>
 #include <linux/netdevice.h>
 #include <linux/netlink.h>
 #include <linux/percpu.h>