carl9170: add missing return-value check

This patch adds a forgotten bail-out path.
Signed-off-by: NChristian Lamparter <chunkeey@googlemail.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/carl9170/phy.c

@@ -1676,6 +1676,8 @@ int carl9170_set_channel(struct ar9170 *ar, struct ieee80211_channel *channel,
 
 	err = carl9170_write_reg(ar, AR9170_PHY_REG_HEAVY_CLIP_ENABLE,
 				 0x200);
+	if (err)
+		return err;
 
 	err = carl9170_init_rf_bank4_pwr(ar,
 		channel->band == IEEE80211_BAND_5GHZ,