parisc/PCI: lba: use pci_create_bus() instead of pci_scan_bus_parented()

No functional change here; just converting from pci_scan_bus_parented()
to pci_create_bus() to make a future patch simpler.

CC: linux-parisc@vger.kernel.org
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>