mac80211: revamp beacon configuration

This patch changes mac80211's beacon configuration handling
to never pass skbs to the driver directly but rather always
require the driver to use ieee80211_beacon_get(). Additionally,
it introduces "change flags" on the config_interface() call
to enable drivers to figure out what is changing. Finally, it
removes the beacon_update() driver callback in favour of
having IBSS beacon delivered by ieee80211_beacon_get() as well.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index ea03010..8e7ba0e 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -469,7 +469,7 @@
 
 	kfree(old);
 
-	return ieee80211_if_config_beacon(sdata->dev);
+	return ieee80211_if_config(sdata, IEEE80211_IFCC_BEACON);
 }
 
 static int ieee80211_add_beacon(struct wiphy *wiphy, struct net_device *dev,
@@ -523,7 +523,7 @@
 	synchronize_rcu();
 	kfree(old);
 
-	return ieee80211_if_config_beacon(dev);
+	return ieee80211_if_config(sdata, IEEE80211_IFCC_BEACON);
 }
 
 /* Layer 2 Update frame (802.2 Type 1 LLC XID Update response) */