Add support for Reston debug interface

Allow to flash the STM32 over the built-in FT230X chip
and use the serial port.

BUG=none
TEST=launch servod, flash_ec and serial console
Change-Id: I7d66ca81a5c28f3989adbee931b163264c914e28
Reviewed-on: https://chromium-review.googlesource.com/174308
Reviewed-by: Todd Broch <tbroch@chromium.org>
Commit-Queue: Vincent Palatin <vpalatin@chromium.org>
Tested-by: Vincent Palatin <vpalatin@chromium.org>
3 files changed