PCI: Simplify pcie_bus_configure_settings() interface

Based on a patch by Jon Mason (see URL below).

All users of pcie_bus_configure_settings() pass arguments of the form
"bus, bus->self->pcie_mpss".  The "mpss" argument is redundant since we
can easily look it up internally.  In addition, all callers check
"bus->self" for NULL, which we can also do internally.

This patch simplifies the interface and the callers.  No functional change.

Reference: http://lkml.kernel.org/r/1317048850-30728-2-git-send-email-mason@myri.com
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

arch/powerpc/kernel/pci-common.c

@@ -1672,12 +1672,8 @@ void pcibios_scan_phb(struct pci_controller *hose)
 	/* Configure PCI Express settings */
 	if (bus && !pci_has_flag(PCI_PROBE_ONLY)) {
 		struct pci_bus *child;
-		list_for_each_entry(child, &bus->children, node) {
-			struct pci_dev *self = child->self;
-			if (!self)
-				continue;
-			pcie_bus_configure_settings(child, self->pcie_mpss);
-		}
+		list_for_each_entry(child, &bus->children, node)
+			pcie_bus_configure_settings(child);
 	}
 }