Add support for Plankton debug interface

Allow to flash the STM32F072 over the built-in FT230X chip
and use the serial port.

BUG=none
TEST=launch servod, flash_ec and serial console

Change-Id: I0d8a1a78cde065b7bb585140de3f11f41cfd2ac1
Signed-off-by: Alec Berg <alecaberg@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/207814
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>
Reviewed-by: Todd Broch <tbroch@chromium.org>
3 files changed