We can easily test this, just like PCI. PHB unplug is not supported
on s390x and x86 ACPI.

Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <155059673939.1466090.14354001937819612724.stgit@bahia.lab.toulouse-stg.fr.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>