This fixes a hard lock that happens when using a second channel on an
in use TCC. The lock occurred when setting the duty cycle on the channel
because the hw address was not available to ASF.
Thanks to @ladyada for finding the bug.
rather than 24bit. Setting the period for more than a 16bit number
caused the TCC to be in a weird state where resetting it would hard
crash.
Fixes#153
This was done to allow greatly granularity when deciding what functionality
is built into each board's build. For example, this way pulseio can be
omitted to allow for something else such as touchio.
