powerpc/PCI: compute I/O space bus-to-resource offset consistently

Make sure we compute CPU addresses (resource start/end) the same way both
when we set up the I/O aperture (hose->io_resource) and when we use
pcibios_bus_to_resource() to convert BAR values into resources.

This fixes a build failure ("cast from pointer to integer of different
size" in configs where resource_size_t is 64 bits but pointers are 32 bits)
I introduced in 6c5705fec63d.

Acked-By: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c
index 910b9de..2efd52d 100644
--- a/arch/powerpc/kernel/pci-common.c
+++ b/arch/powerpc/kernel/pci-common.c
@@ -1492,6 +1492,11 @@
 	return pci_enable_resources(dev, mask);
 }
 
+resource_size_t pcibios_io_space_offset(struct pci_controller *hose)
+{
+	return (unsigned long) hose->io_base_virt - _IO_BASE;
+}
+
 static void __devinit pcibios_setup_phb_resources(struct pci_controller *hose, struct list_head *resources)
 {
 	struct resource *res;
@@ -1516,8 +1521,7 @@
 		 (unsigned long long)res->start,
 		 (unsigned long long)res->end,
 		 (unsigned long)res->flags);
-	pci_add_resource_offset(resources, res,
-			(resource_size_t) hose->io_base_virt - _IO_BASE);
+	pci_add_resource_offset(resources, res, pcibios_io_space_offset(hose));
 
 	/* Hookup PHB Memory resources */
 	for (i = 0; i < 3; ++i) {