PCI: constify pci_bus_assign_resources()

drivers/pci/hotplug/fakephp.c: In function 'pci_rescan_bus':
drivers/pci/hotplug/fakephp.c:271: warning: passing argument 1 of 'pci_bus_assign_resources' discards qualifiers from pointer target type

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