Add input-pwm support along with platform tweaks for Gumstix AeroCore

This driver probably still has too much left over from the sensor driver you based it on.

I do have some reservations about the design in general; the hardware-specific side should be collecting and pushing channel sets based on the input frame rate (pick a valid channel that paces the input, push each time a new frame starts on that channel, etc.)

There's no need for the workq in that case...