case closed debug: Add Ryu CCD support

Add EC_PD with EC3PO and AP CCD UART support for Ryu,
for use with Servo V4.

BUG=chromium:571476
TEST=sudo servod -c ccd_ryu.xml; miniterm to both consoles.

Change-Id: Ic5392a3055f741422d81f125294006cddff62f85
Signed-off-by: Nick Sanders <nsanders@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/338252
Reviewed-by: Aseda Aboagye <aaboagye@chromium.org>
Reviewed-by: Todd Broch <tbroch@chromium.org>
3 files changed