mac80211: ensure we don't update tx power on a non-running sdata

commit 5ad11b50 upstream.

We can't update the Tx power on the device unless it is
running.

This fixes https://bugzilla.kernel.org/show_bug.cgi?id=101521.
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

net/mac80211/iface.c

@@ -74,7 +74,8 @@ bool __ieee80211_recalc_txpower(struct ieee80211_sub_if_data *sdata)
 
 void ieee80211_recalc_txpower(struct ieee80211_sub_if_data *sdata)
 {
-	if (__ieee80211_recalc_txpower(sdata))
+	if (__ieee80211_recalc_txpower(sdata) ||
+	    ieee80211_sdata_running(sdata))
 		ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_TXPOWER);
 }