o acpi_hpet: auto-added 'wildcard' devices can be identified by
non-NULL handle attribute.
o acpi_ec: auto-add 'wildcard' devices can be identified by
unset (NULL) private attribute.
o acpi_cpu: use private instead of magic to store cpu id.
Reviewed by: jhb
Silence from: acpi@
MFC after: 2 weeks
X-MFC-Note: perhaps the ivar should stay for ABI stability