r8169: fix WoL device wakeup enable

In rtl8169_runtime_resume() we configure WoL but don't set the device
to wakeup-enabled. This prevents PME generation once the cable is
re-plugged. Fix this by moving the call to device_set_wakeup_enable()
to __rtl8169_set_wol().

Fixes: 433f9d0d

 ("r8169: improve saved_wolopts handling")
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>