r8169: remember WOL preferences on driver load

Do not clear Broadcast/Multicast/Unicast Wake Flag or LanWake in
Config5. This is necessary to preserve WOL state when the driver is
loaded. Although the r8168 vendor driver does not write Config5 (it has
been commented out), Hayes Wang from Realtek said that masking bits like
this is more sensible.

Signed-off-by: Peter Wu <lekensteyn@gmail.com>
Acked-by: Francois Romieu <romieu@fr.zoreil.com>
Signed-off-by: David S. Miller <davem@davemloft.net>