x86: disable apm on the olpc

The OLPC doesn't support APM but also doesn't have DMI, so we can't detect
and disable it based on DMI data.  So, just disable based on machine_is_olpc()

Signed-off-by: Jeremy Katz <katzj@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>