cfg80211/mac80211: use reduced txpower for 5 and 10 MHz

Some regulations (like germany, but also FCC) express their transmission
power limit in dBm/MHz or mW/MHz. To cope with that and be on the safe
side, reduce the maximum power to half (10 MHz) or quarter (5 MHz)
when operating on these reduced bandwidth channels.

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Mathias Kretschmer <mathias.kretschmer@fokus.fraunhofer.de>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index 091088a..6da98c7 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -151,7 +151,7 @@
 		changed |= IEEE80211_CONF_CHANGE_SMPS;
 	}
 
-	power = chandef.chan->max_power;
+	power = ieee80211_chandef_max_power(&chandef);
 
 	rcu_read_lock();
 	list_for_each_entry_rcu(sdata, &local->interfaces, list) {