Add and entry for the Intel i82545GM with external PHY which works fine:

wm0 at pci1 dev 1 function 0: Intel i82545GM 1000BASE-T Ethernet, rev. 4
wm0: interrupting at ivec 0
wm0: 64-bit 66MHz PCI bus
wm0: 256 word (8 address bits) MicroWire EEPROM
wm0: Ethernet address 00:04:23:xx:xx:xx
makphy0 at wm0 phy 1: Marvell 88E1011 Gigabit PHY, rev. 5

(tron)