powerpc/PCI: Use list_for_each_entry() for bus traversal

Replace list_for_each() + pci_bus_b() with list_for_each_entry().

Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

arch/powerpc/kernel/pci_64.c

@@ -208,7 +208,6 @@ long sys_pciconfig_iobase(long which, unsigned long in_bus,
 			  unsigned long in_devfn)
 {
 	struct pci_controller* hose;
-	struct list_head *ln;
 	struct pci_bus *bus = NULL;
 	struct device_node *hose_node;
 
@@ -230,8 +229,7 @@ long sys_pciconfig_iobase(long which, unsigned long in_bus,
 	 * used on pre-domains setup. We return the first match
 	 */
 
-	for (ln = pci_root_buses.next; ln != &pci_root_buses; ln = ln->next) {
-		bus = pci_bus_b(ln);
+	list_for_each_entry(bus, &pci_root_buses, node) {
 		if (in_bus >= bus->number && in_bus <= bus->busn_res.end)
 			break;
 		bus = NULL;