The AR934x and later (which will turn up eventually) have a new GPIO
output configuration option - a real MUX rather than a "GPIO or this
function."
For now I'm squirreling it away in the CPU code just so it's done -
I may move this to the GPIO layer later.
Specifically, this is required for setting up some boards that have
external receive side LNA (low noise amplifier) that gets switched on/off
by the on-chip wireless MAC. If we don't add this support for those
boards then we'll end up with really poor performance.
(I don't yet have one of those APs, but it'll likely show up in a week.)
Obtained from: Linux OpenWRT
92005e6093