sr9800: 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: 19a38d8e ("USB2NET : SR9800 : One chip USB2.0 USB2NET SR9800 Device Driver Support")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>