platform/chrome: chros_ec_ishtp: only load for matching devices

Previously it was loaded for all ISHTP devices.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>