PCI hotplug: cpqphp: fix kernel NULL pointer dereference

The following patch fixes the regression in 2.6.27 that causes kernel
NULL pointer dereference at cpqphp driver probe time.  This patch should
be backported to the .27 stable series.

Seems to have been introduced by
f46753c5

.

The root cause of this problem seems that cpqphp driver calls
pci_hp_register() wrongly. In current implementation, cpqphp driver
passes 'ctrl->pci_dev->subordinate' as a second parameter for
pci_hp_register(). But because hotplug slots and it's hotplug controller
(exists as a pci funcion) are on the same bus, it should be
'ctrl->pci_dev->bus' instead.

Cc: <stable@kernel.org>
Tested-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>