PCI: add acpi_find_root_bridge_handle

Consolidate finding of a root bridge and getting its handle to the one
inline function. It's cut & pasted on multiple places. Use this new
inline in those.

Cc: kristen.c.accardi@intel.com
Acked-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
diff --git a/drivers/pci/hotplug/acpi_pcihp.c b/drivers/pci/hotplug/acpi_pcihp.c
index bd83197..e17ef54 100644
--- a/drivers/pci/hotplug/acpi_pcihp.c
+++ b/drivers/pci/hotplug/acpi_pcihp.c
@@ -404,10 +404,7 @@
 	 * OSHP within the scope of the hotplug controller and its parents,
 	 * upto the host bridge under which this controller exists.
 	 */
-	while (pdev->bus->self)
-		pdev = pdev->bus->self;
-	handle = acpi_get_pci_rootbridge_handle(pci_domain_nr(pdev->bus),
-			pdev->bus->number);
+	handle = acpi_find_root_bridge_handle(pdev);
 	if (handle) {
 		acpi_get_name(handle, ACPI_FULL_PATHNAME, &string);
 		dbg("Trying to get hotplug control for %s\n",