hwmon: (adm1029) Use mask for fan_div value

This is my patch for testing correct values of fan div in adm1029 and
prevent a division by 0 for some (unlikely) register values.
Signed-off-by: NCorentin Labbe <corentin.labbe@geomatys.fr>
Signed-off-by: NJean Delvare <khali@linux-fr.org>

drivers/hwmon/adm1029.c

@@ -179,7 +179,8 @@ show_fan(struct device *dev, struct device_attribute *devattr, char *buf)
 	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
 	struct adm1029_data *data = adm1029_update_device(dev);
 	u16 val;
-	if (data->fan[attr->index] == 0 || data->fan_div[attr->index] == 0
+	if (data->fan[attr->index] == 0
+	    || (data->fan_div[attr->index] & 0xC0) == 0
 	    || data->fan[attr->index] == 255) {
 		return sprintf(buf, "0\n");
 	}
@@ -194,7 +195,7 @@ show_fan_div(struct device *dev, struct device_attribute *devattr, char *buf)
 {
 	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
 	struct adm1029_data *data = adm1029_update_device(dev);
-	if (data->fan_div[attr->index] == 0)
+	if ((data->fan_div[attr->index] & 0xC0) == 0)
 		return sprintf(buf, "0\n");
 	return sprintf(buf, "%d\n", DIV_FROM_REG(data->fan_div[attr->index]));
 }