asix: Check for supported Wake-on-LAN modes

The driver currently silently accepts unsupported Wake-on-LAN modes
(other than WAKE_PHY or WAKE_MAGIC) without reporting that to the user,
which is confusing.

Fixes: 2e55cc72 ("[PATCH] USB: usbnet (3/9) module for ASIX Ethernet adapters")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>