hwmon: (ds1621) Update zbits after conversion rate change

After the conversion rate is changed, the zbits are not updated,
but should be, since they are used later in the set_temp function.

Fixes: a50d9a4d9ad3 ("hwmon: (ds1621) Fix temperature rounding operations")
Reported-by: Murat Ilsever <murat.ilsever@gmail.com>
Signed-off-by: Robert Coulson <rob.coulson@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/ds1621.c

@@ -309,6 +309,7 @@ static ssize_t set_convrate(struct device *dev, struct device_attribute *da,
 	data->conf |= (resol << DS1621_REG_CONFIG_RESOL_SHIFT);
 	i2c_smbus_write_byte_data(client, DS1621_REG_CONF, data->conf);
 	data->update_interval = ds1721_convrates[resol];
+	data->zbits = 7 - resol;
 	mutex_unlock(&data->update_lock);
 
 	return count;