platform/chrome: cros_ec_typec: Use notifier for updates

Register a listener for the cros-usbpd-notifier, and update port state
when a notification comes in.

Signed-off-by: Prashant Malani <pmalani@chromium.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>