platform/chrome: cros_usbpd_notify: Pull PD_HOST_EVENT status

Read the PD host even status from the EC and send that to the notifier
listeners, for more fine-grained event information.

Signed-off-by: Prashant Malani <pmalani@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Benson Leung <bleung@chromium.org>