Move the contents of power_state_controller.py to servo.py.

After recent refactoring, the content of the power_state_controller
module is compact enough to be private to the servo module.  This
makes it so.

BUG=chromium:326738
TEST=FAFTSetup, platform_ServoPowerStateController

Change-Id: I5215a9709ed4e64251ca5b980112720bfe63a964
Reviewed-on: https://chromium-review.googlesource.com/203496
Tested-by: Richard Barnette <jrbarnette@chromium.org>
Reviewed-by: Dan Shi <dshi@chromium.org>
Commit-Queue: Richard Barnette <jrbarnette@chromium.org>
2 files changed