mac80211: remove ARP filter enable/disable logic

Depending on the driver, having ARP filtering for
some addresses may be possible. Remove the logic
that tracks whether ARP filter is enabled or not
and give the driver the total number of addresses
instead of the length of the list so it can make
its own decision.

Reviewed-by: Luciano Coelho <coelho@ti.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/ieee80211_i.h

@@ -747,8 +747,6 @@ struct ieee80211_sub_if_data {
 	struct work_struct work;
 	struct sk_buff_head skb_queue;
 
-	bool arp_filter_state;
-
 	u8 needed_rx_chains;
 	enum ieee80211_smps_mode smps_mode;