gma500: don't register the ACPI video bus

commit 155689defc782b486a7e6776a57ecc4ebb37ed52 upstream.

We are not yet ready for this and it makes a mess on some devices.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>