PCI: deprecate pci_scan_bus_parented()

Users of pci_scan_bus_parented() should be converted to use either
    pci_scan_root_bus() (preferred, but also calls pci_bus_add_devices)
or
    pci_create_root_bus()
    pci_scan_child_bus()

Since pci_scan_bus_parented(), I'm marking it deprecated now and will
actually remove it later.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>