Staging: batman-adv: Remove currently unused gw_* datastructures

gw_list_lock, gw_list and curr_gw are currently unused members of struct
bat_priv. They will be readded when gateway support is really
implemented.

Signed-off-by: Sven Eckelmann <sven.eckelmann@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>