net: wan: remove support for Z85230-based devices

Looks like all the changes to this driver had been automated
churn since git era begun. The driver is using virt_to_bus(),
it's just a maintenance burden unlikely to have any users.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>