platform/chrome: chromeos_tbmc: Check ACPI_COMPANION()

platform/chrome: chromeos_tbmc: Check ACPI_COMPANION()

Every platform driver can be forced to match a device that doesn't match
its list of device IDs because of device_match_driver_override(), so
platform drivers that rely on the existence of a device's ACPI companion
object need to verify its presence.

Accordingly, add a requisite ACPI_COMPANION() check against NULL to the
chromeos_tbmc driver.

Fixes: a2676ead257f ("platform/chrome: chromeos_tbmc: Convert to a platform driver")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/1875121.VLH7GnMWUR@rafael.j.wysocki
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>