usbnet: Remove over-broad module alias from zaurus.

This module and a bunch of dependancies are getting loaded on several
of laptops I have (probably picking up the mobile broadband device),
that have nothing to do with zaurus. Matching by class without
any vendor/device pair isn't the right thing to do here, as it
will prevent any other driver from correctly binding to it.
(Or in the absense of a driver, will just waste time & memory by
 unnecessarily loading modules)

Signed-off-by: Dave Jones <davej@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>