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>
diff --git a/drivers/pci/hotplug/pcihp_slot.c b/drivers/pci/hotplug/pcihp_slot.c
index fec2d5b..16f9203 100644
--- a/drivers/pci/hotplug/pcihp_slot.c
+++ b/drivers/pci/hotplug/pcihp_slot.c
@@ -160,9 +160,8 @@
 			(dev->class >> 8) == PCI_CLASS_BRIDGE_PCI)))
 		return;
 
-	if (dev->bus && dev->bus->self)
-		pcie_bus_configure_settings(dev->bus,
-					    dev->bus->self->pcie_mpss);
+	if (dev->bus)
+		pcie_bus_configure_settings(dev->bus);
 
 	memset(&hpp, 0, sizeof(hpp));
 	ret = pci_get_hp_params(dev, &hpp);