iwlwifi: indicate txpower is off in sysfs

The patch checks if the radio is disabled before displaying the tx power
level. Previously when the txpower was set off show_tx_power still
returned the prior power level. Now it will indicate the power has been
turned off.
Signed-off-by: NJay Sternberg <jay.e.sternberg@linux.intel.com>
Signed-off-by: NZhu Yi <yi.zhu@intel.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-agn.c

@@ -3418,7 +3418,11 @@ static ssize_t show_tx_power(struct device *d,
 			     struct device_attribute *attr, char *buf)
 {
 	struct iwl_priv *priv = (struct iwl_priv *)d->driver_data;
-	return sprintf(buf, "%d\n", priv->tx_power_user_lmt);
+
+	if (!iwl_is_ready_rf(priv))
+		return sprintf(buf, "off\n");
+	else
+		return sprintf(buf, "%d\n", priv->tx_power_user_lmt);
 }
 
 static ssize_t store_tx_power(struct device *d,