em broken on current amd64

[Garrett Cooper]

> On Sep 5, 2015, at 08:50, Manfred Antar <null at pozo.com> wrote:
> 
> 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

Tijl said the same. The offending commit's r287467.
Cheers,