batman-adv: Drop unused lockdep include

The commit dee222c7 ("batman-adv: Move OGM rebroadcast stats to
orig_ifinfo") removed all used functionality of the include linux/lockdep.h
from batadv_iv_ogm.c.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>