ipmi: add an NPCM7xx KCS BMC driver

This driver exposes the Keyboard Controller Style (KCS) interface on
Novoton NPCM7xx SoCs as a character device. Such SOCs are commonly used
as a BaseBoard Management Controller (BMC) on a server board, and KCS
interface is commonly used to perform the in-band IPMI communication
between the server and its BMC.

Signed-off-by: Avi Fishman <avifishman70@gmail.com>
Signed-off-by: Haiyue Wang <haiyue.wang@linux.intel.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>