tilepro pci: fix pci_bus.subordinate bad bombing from b918c62e

The bombing to convert pci_bus.subordinate to busn_res.end accidentally
modified a "struct pci_dev" site, causing this file not to compile.
This commit reverts that code to use dev->subordinate again.
Signed-off-by: NChris Metcalf <cmetcalf@tilera.com>

arch/tile/kernel/pci.c

@@ -369,7 +369,7 @@ int __init pcibios_init(void)
 				 */
 				if ((dev->class >> 8) == PCI_CLASS_BRIDGE_PCI &&
 					(PCI_SLOT(dev->devfn) == 0)) {
-					next_bus = dev->busn_res.end;
+					next_bus = dev->subordinate;
 					controllers[i].mem_resources[0] =
 						*next_bus->resource[0];
 					controllers[i].mem_resources[1] =