mac80211: keep a separate list of monitor interfaces that are up

In addition to keeping monitor interfaces on the regular list of
interfaces, keep those that are up and not in cooked mode on a
separate list. This saves having to iterate all interfaces when
delivering to monitor interfaces.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/ieee80211_i.h

@@ -839,6 +839,8 @@ struct txq_info {
 struct ieee80211_if_mntr {
 	u32 flags;
 	u8 mu_follow_addr[ETH_ALEN] __aligned(2);
+
+	struct list_head list;
 };
 
 /**
@@ -1259,6 +1261,7 @@ struct ieee80211_local {
 
 	/* see iface.c */
 	struct list_head interfaces;
+	struct list_head mon_list; /* only that are IFF_UP && !cooked */
 	struct mutex iflist_mtx;
 
 	/*