ath6kl: Unset IFF_LOWER_UP flag on AP mode leave.

When disabling tethering after having enabled it, the ath6kl driver does
not set the IFF_LOWER_UP flag to 0 (carrier off) on the wlan interface.

The upper layers (eg. connman) are not notified of the tethering mode
status change. So, tethering can not be activated anymore.

This patch adds a netif_carrier_off() call when stopping AP mode to fix
the problem.
Signed-off-by: NPierre Le Magourou <plemagourou@aldebaran.com>
Signed-off-by: NKalle Valo <kvalo@qca.qualcomm.com>

drivers/net/wireless/ath/ath6kl/cfg80211.c

@@ -2979,6 +2979,7 @@ static int ath6kl_stop_ap(struct wiphy *wiphy, struct net_device *dev)
 
 	ath6kl_wmi_disconnect_cmd(ar->wmi, vif->fw_vif_idx);
 	clear_bit(CONNECTED, &vif->flags);
+	netif_carrier_off(vif->ndev);
 
 	/* Restore ht setting in firmware */
 	return ath6kl_restore_htcap(vif);