platform/x86: drop deprecated asus_acpi driver

asus_acpi only support old models, it has been deprecated since
2009 in favor of asus-laptop, it's not built by any (sane) distro,
so it is time to say good bye.

Thanks to Julien Lerouge and Karol Kozimor for the work they have
done on it, I would never have wrote asus-laptop and other asus
related drivers without asus_acpi.

Signed-off-by: Corentin Chary <corentin.chary@gmail.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>