PCI: Simplify MPS test for Downstream Port

PCIe hotplug bridges are always either Root Ports or Downstream Ports.  No
other device type can have a PCIe link leading downstream to a slot.

Root Ports don't have an upstream bridge, so "dev->is_hotplug_bridge &&
dev->bus->self" is true if and only if "dev" is a Downstream Port.  That
means we can simplify this by looking at the type of "dev" itself, without
looking upstream at all.

No functional change.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/probe.c

@@ -1507,8 +1507,7 @@ static int pcie_find_smpss(struct pci_dev *dev, void *data)
 	 * will occur as normal.
 	 */
 	if (dev->is_hotplug_bridge && (!list_is_singular(&dev->bus->devices) ||
-	     (dev->bus->self &&
-	      pci_pcie_type(dev->bus->self) != PCI_EXP_TYPE_ROOT_PORT)))
+	    pci_pcie_type(dev) != PCI_EXP_TYPE_ROOT_PORT))
 		*smpss = 0;
 
 	if (*smpss > dev->pcie_mpss)