net: phy: marvell: don't use empty switch default case

This causes error reported by kernel test robot.
Signed-off-by: Marek Behún <kabel@kernel.org>
Fixes: 41d26bf4 ("net: phy: marvell: refactor HWMON OOP style")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/marvell.c

@@ -2499,8 +2499,6 @@ static int marvell_hwmon_write(struct device *dev, enum hwmon_sensor_types type,
 		if (ops->set_temp_critical)
 			err = ops->set_temp_critical(phydev, temp);
 		break;
-	default:
-		fallthrough;
 	}
 
 	return err;