With this change, the driver tests good (at least on i386):
wb0: <Winbond W89C840F 10/100BaseTX> port 0xb800-0xb87f mem 0xe6800000-0xe680007f irq 12 at device 10.0 on pci0
miibus1: <MII bus> on wb0
amphy0: <Am79C873 10/100 media interface> on miibus1
amphy0: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
wb0: Ethernet address: 00:00:e8:18:2a:02
wb0: link state changed to DOWN
wb0: link state changed to UP