ath9k: add per-vif TX power capability

Configure the HW with highest TX power among all vif when HW TPC has been
enabled in order to add support to per-vif TX power capability. Use lowest
configured power among all interfaces when TPC is disabled

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
diff --git a/drivers/net/wireless/ath/ath9k/debug.c b/drivers/net/wireless/ath/ath9k/debug.c
index 50a2e0a..dbf8f49 100644
--- a/drivers/net/wireless/ath/ath9k/debug.c
+++ b/drivers/net/wireless/ath/ath9k/debug.c
@@ -1156,7 +1156,10 @@
 
 	if (tpc_enabled != ah->tpc_enabled) {
 		ah->tpc_enabled = tpc_enabled;
-		ath9k_hw_set_txpowerlimit(ah, sc->cur_chan->txpower, false);
+
+		mutex_lock(&sc->mutex);
+		ath9k_set_txpower(sc, NULL);
+		mutex_unlock(&sc->mutex);
 	}
 
 	return count;