APUv2/v3 board support V3

From: Enrico Weigelt, metux IT consult
Date: Thu Feb 14 2019 - 17:05:30 EST

Hi folks,

this is version 3 of my APUv2/APUv3 series.

change in V3:

* gpio driver
* drop unncessary gpio id checks
* cleanup amd_fch_gpio_set()
* move iores outside probe()
* shorter NULL checks and correct error in probe()
* apu board driver
* drop unneeded init.h
* drop unnecessary comments
* clean up logging
* dont need to depend on KEYBOARD_GPIO