servod: add chatty sleep information

This may come in handy debgging timing issues in the future.

BUG=b:38448364
TEST=None

Change-Id: Ie456214d0ec104a5f90f7d52dd7a56f5e5f3ad06
Reviewed-on: https://chromium-review.googlesource.com/989294
Commit-Ready: Nick Sanders <nsanders@chromium.org>
Tested-by: Nick Sanders <nsanders@chromium.org>
Reviewed-by: Aseda Aboagye <aaboagye@chromium.org>
1 file changed