This option enables/disables PCI hotplug for a particular PHB.

Also add machine compatibility code to disable it by default for machine
types prior to pseries-2.4.
Signed-off-by: NMichael Roth <mdroth@linux.vnet.ibm.com>
Reviewed-by: NDavid Gibson <david@gibson.dropbear.id.au>
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>
[agraf: move commas for compat fields]
Signed-off-by: NAlexander Graf <agraf@suse.de>