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/iface.c b/net/mac80211/iface.c
index cc11759..4c41c11 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -54,7 +54,7 @@
 		return false;
 	}
 
-	power = chanctx_conf->def.chan->max_power;
+	power = ieee80211_chandef_max_power(&chanctx_conf->def);
 	rcu_read_unlock();
 
 	if (sdata->user_power_level != IEEE80211_UNSET_POWER_LEVEL)