[coreboot] Supermicro H8QME-2+ mct_d fatal exit.

[ron minnich]

Just FYI:

on our first system with Arima boards in 2002, everything worked well
until we started booting 64-bit kernels. I'm not kidding. We did not
find the SMBUS MUX on the boards until we had unreliable coreboot
boots of 64-bit kernels. For quite some time the boards worked fine.
Ollie found the SMBUS MUX by examining schematics.

So the SMBUS mux can appear in strange ways, at strange times. This
sounds like one of those times. SMBUS muxes are more common than you
might think and the default power-on state is not always very well
determined.

ron