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 <[e-mail]>
Signed-off-by: Robert Coulson <[e-mail]>
Cc: [e-mail]
Signed-off-by: Guenter Roeck <[e-mail]>

drivers/hwmon/ds1621.c

···
 	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;