eth: de4x5: remove support for Generic DECchip & DIGITAL EtherWORKS PCI/EISA

Looks like almost all changes to this driver had been tree-wide
refactoring since git era begun. There is one commit from Al
15 years ago which could potentially be fixing a real bug.

The driver is using virt_to_bus() and is a real magnet for pointless
cleanups. It seems unlikely to have real users. Let's try to shed
this maintenance burden.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>