r8169: use phy_resume/phy_suspend

Use phy_resume() / phy_suspend() instead of open coding this functionality.
The chip version specific differences are handled by the respective PHY
drivers.

The call to r8168_phy_power_down() in r8168_pll_power_down() can be
removed because phylib takes care now. The relevant scenarios are:
- rtl8169_close(): phy_disconnect() powers down PHY
- suspend: mdio_bus_phy_suspend() takes care
- runtime-suspend: WoL is active, don't suspend PHY
- rtl_shutdown(): no need to power down PHY

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>