em broken on current amd64

Sat Sep 5 15:50:58 UTC 2015

Recent changes to em have broken current on amd64.
Booting kernel will hang when trying to load em0, then will continue booting without the driver loading (No Network)
This is on a HP SFF 8000 with em0 embedded on the motherboard.

boot messages:

em0: <Intel(R) PRO/1000 Network Connection 7.5.2> port 0x3100-0x311f mem 0xf3100000-0xf311ffff,0xf3125000-0xf3125fff irq 19 at device 25.0 on pci0
em0: attempting to allocate 1 MSI vectors (1 supported)
em0: using IRQ 265 for MSI
em0: Using an MSI interrupt
em0: The EEPROM Checksum Is Not Valid
device_attach: em0 attach returned 5

Manfred