[coreboot] [v2][patch] add SMSC SCH3112 superio

[Chris Kilgour]

This trivial patch adds the SMSC SCH3112 superio chip ID to the generic 
SMSC support, and corrects a small typo.
With this patch, coreboot v2 on a mainboard with SCH3112 has been 
demonstrated to correctly use the serial port.  No other chip functions 
were tested.

Signed-off-by: Christopher Kilgour