PCI: constify pci_bus_add_devices()

drivers/pci/hotplug/fakephp.c:283: warning: passing argument 1 of 'pci_bus_add_devices' discards qualifiers from pointer target type

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>