r8169: WoL fixes, part 2.

Since recent kernel (2.6.26 or 2.6.27) the PCI wakeup functions are
influenced by generic device ability and configuration when enabling
PCI-device triggered wake-up.

This patch causes WoL setting to enable/disable device's wish to
be permitted to wake-up the host when changing WoL options and
also during device probing.

Without this patch one has write 'enabled' to
  /sys/bus/pci/devices/0000:02:08.0/power/wakeup

Signed-off-by: Bruno Prémont <bonbons@linux-vserver.org>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>