platform/chrome: cros_ec_types: Support disconnect events without partners

There are certain scenarios, where a disconnect event might
occur on a Type-C port with no port partners. This is required
to enable communication to Burnside Bridge USB4 retimers.

Signed-off-by: Rajmohan Mani <rajmohan.mani@intel.com>
Reviewed-by: Prashant Malani <pmalani@chromium.org>
Link: https://lore.kernel.org/r/20210205195113.20277-3-rajmohan.mani@intel.com


Signed-off-by: Benson Leung <bleung@chromium.org>