platform/chrome: chromeos_laptop: drop checks of NULL-safe functions

No need to check the argument of i2c_unregister_device() and
property_entries_free() because the functions do check it.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>