ath9k: Fix bug in determining calibration support

ADC gain calibration has to be done for all non 2GHZ-HT20 channels.
Regression from "ath9k: use ieee80211_conf on ath9k_hw_iscal_supported()"

Cc: stable@kernel.org
Signed-off-by: NSujith <Sujith.Manoharan@atheros.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/calib.c

@@ -284,8 +284,8 @@ static bool ath9k_hw_iscal_supported(struct ath_hw *ah,
 		return true;
 	case ADC_GAIN_CAL:
 	case ADC_DC_CAL:
-		if (conf->channel->band == IEEE80211_BAND_5GHZ &&
-		  conf_is_ht20(conf))
+		if (!(conf->channel->band == IEEE80211_BAND_2GHZ &&
+		      conf_is_ht20(conf)))
 			return true;
 		break;
 	}