configure the mux and config registers for PIO devices based on what
we find in the FDT. I developed it per the spec that had been
committed to Linux in the January 2014 time frame and haven't
updated. In short, bundles of pins are activated in specific ways for
specific configurations, and we implement all of that.
What's not included is a MI device infrastructure, any dynamic
run-time changing of these pins, etc. Also not included are hooks into
all the drivers to enable the latter (static at boot no driver changes
are needed). These larger questions will need to be answered once we
have more drivers like this for more platforms, or somebody has a heck
of a lot of time to research a bunch of platforms, the Linux solution
(which is good, but has its warts), etc.
