platform/chrome: cros_ec_typec: Clear partner identity on device removal

The partner identity struct isn't reset when a partner is removed,
meaning a subsequent partner can inherit an old partner's identity VDOs
before discovery is complete. So, clear that struct when a partner
removal is detected.

Signed-off-by: Prashant Malani <pmalani@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Link: https://lore.kernel.org/r/20201029222738.482366-4-pmalani@chromium.org