Forward Port of ftdi-sio GPIO Patch to Recent Kernel

I've been working on a magnetic door lock controller for Unlab (the hackerspace in London, ON). It may end up being deployed on a Raspberry Pi, but those are quite expensive for the use case. In any case, I develop on a normal linux machine and wanted to avoid the RPi.GPIO module that is specific to the Pi.

For testing I wanted to use the FT232R on my Adafruit FTDI Friend via the sysfs GPIO interface. There are several patches (of various qualities) that support this, but none of them are on track to be mainlined. I chose the best looking one and found that the gpiolib interface has changed somewhat. I forward ported Sacha Silbe's patch to 4.7; it's available at github: https://gist.github.com/nocko/6d0b9ec56d6b1b602e964e56f48c9a4b