platform/chrome: cros_ec_proto: add "cros_ec_" prefix to send_command()

To be neat, add "cros_ec_" prefix to static function send_command().

Reviewed-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Link: https://lore.kernel.org/r/20220718050914.2267370-3-tzungbi@kernel.org