Generate some square pulses using the Overo PWM outputs with a slow frequency
and very small duty cycle.

For example, I want a 100 usec signal on PWM8 and a 150 usec signal on PWM9
that starts 20 usec after the PWM8 signal.

          ___________
         |           |
PWM8 ____|           |___________________________________________

            ________________
           |                |
PWM9 ______|                |____________________________________


The driver is a kernel module that allows me to control the PWM timers
to get this kind of behavior.  

The control program will provide a simpler interface to the kernel
module.

This is for generating some test signals for some other equipment
I am working on, but this piece is pretty generic.