EC sync: Drop support for "PD" software sync.

All devices which have a PD chip running CrOS EC code have already shipped,
and there is no intention to go back to using an "EC" for a TCPC anymore.

BUG=b:143762298,chromium:1017093
BRANCH=none
TEST=make runtests

Change-Id: I177c00581089de59e4f35608b97ef5432e8b492b
Signed-off-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/1895712
Tested-by: Joel Kitching <kitching@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Joel Kitching <kitching@chromium.org>
7 files changed