batman-adv: Remove unnecessary lockdep in batadv_mcast_mla_list_free

batadv_mcast_mla_list_free() just frees some leftovers of a local feast
in batadv_mcast_mla_update(). No lockdep needed as it has nothing to do
with bat_priv->mcast.mla_list.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>