MAINTAINERS: update maintainers of chrome-platform

Add Tzung-Bi as a maintainer of chrome-platform.

Reviewed-by: Guenter Roeck <groeck@chromium.org>
Link: https://lore.kernel.org/r/20230803100846.3223564-1-tzungbi@kernel.org


Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>