[coreboot] [superiotool] patch for smsc mec1308

[David Hendricks]

Hi,
Attached is a patch to add support for the SMSC MEC1308 embedded controller.

Unfortunately, the device ID it conflicts with another SMSC Super IO chip,
the FDC37M81x. However, since superiotool does not really support the
FDC37M81x in any really useful capacity, I think it's fair to just disable
it for now.

Signed-off-by: David Hendricks