x86/PCI: Drop pcibios_scan_root() check for bus already scanned

The PCI core checks to see whether we've already scanned a bus, so we don't
need to do it in pcibios_scan_root().  Here's where it happens in the core:

  pcibios_scan_root
    pci_scan_bus_on_node
      pci_scan_root_bus
        pci_create_root_bus
	  b2 = pci_find_bus(pci_domain_nr(b), bus)
	  if (b2)
	    goto err_out;    # already scanned this bus

This removes the check from pcibios_scan_root().
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

arch/x86/pci/common.c

@@ -458,15 +458,6 @@ void __init dmi_check_pciprobe(void)
 
 struct pci_bus *pcibios_scan_root(int busnum)
 {
-	struct pci_bus *bus = NULL;
-
-	while ((bus = pci_find_next_bus(bus)) != NULL) {
-		if (bus->number == busnum) {
-			/* Already scanned */
-			return bus;
-		}
-	}
-
 	return pci_scan_bus_on_node(busnum, &pci_root_ops,
 					get_mp_bus_to_node(busnum));
 }