superio/nuvoton: Add Nuvoton NCT6791D

This adds support for Nuvoton NCT6791D Super I/O chips.
Makes use of the common Nuvoton early_serial.c.

Based on the Datasheet supplied by Nuvoton.
Datasheet Version: January 8th, 2016 Revision 1.11

Change-Id: I027d33b85f0dc6ee50deebdccaecc74487eecb40
Signed-off-by: Omar Pakker <omarpakker+coreboot@gmail.com>
Reviewed-on: https://review.coreboot.org/15967
Tested-by: build bot (Jenkins)
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
5 files changed