[RFC/RFT] the new ksetting methods in subnet's subdrivers

[Oliver Neukum]

The API for ethtool has been changed. Rather than implement the change
sparately in each subdriver, usbnet should be changed and the subdrivers
should expand upon the generic method usbnet provides.
This set implements the new methods, introduces them into the subdrivers
and rips out the old stuff, lest it be used in new drivers.