This Microcontroller is present on the Khadas VIM1, VIM2, VIM3 and Edge
boards.

It has multiple boot control features like password check, power-on
options, power-off control and system FAN control on recent boards.

This implements a very basic MFD driver with the fan control and User
NVMEM cells.
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>