tilegx pci: fix semantic merge conflict with 3527ed81

Yinghai Lu removed pci_bus.subordinate in pci-next, which meant that
the tile-next changes to add tilegx PCI support don't build.  This
was expected (seen in linux-next) and this one-line fix is along
the same lines as commit b918c62e for all other architectures.
Acked-by: NBjorn Helgaas <bhelgaas@google.com>
Signed-off-by: NChris Metcalf <cmetcalf@tilera.com>

arch/tile/kernel/pci_gx.c

@@ -853,7 +853,7 @@ int __init pcibios_init(void)
 		bus = pci_scan_root_bus(NULL, next_busno, controller->ops,
 					controller, &resources);
 		controller->root_bus = bus;
-		next_busno = bus->subordinate + 1;
+		next_busno = bus->busn_res.end + 1;
 
 	}