lan78xx: Check for supported Wake-on-LAN modes

The driver supports a fair amount of Wake-on-LAN modes, but is not
checking that the user specified one that is supported.

Fixes: 55d7de9d ("Microchip's LAN7800 family USB 2/3 to 10/100/1000 Ethernet device driver")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Woojung Huh <Woojung.Huh@Microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>