PCI: Make pcie_find_root_port() work for Root Ports

Commit 6ae72bfa ("PCI: Unify pcie_find_root_port() and
pci_find_pcie_root_port()") broke acpi_pci_bridge_d3() because calling
pcie_find_root_port() on a Root Port returned NULL when it should return
the Root Port, which in turn broke power management of PCIe hierarchies.

Rework pcie_find_root_port() so it returns its argument when it is already
a Root Port.

[bhelgaas: test device only once, test for PCIe]
Fixes: 6ae72bfa ("PCI: Unify pcie_find_root_port() and pci_find_pcie_root_port()")
Link: https://lore.kernel.org/r/20200622161248.51099-1-mika.westerberg@linux.intel.comSigned-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

include/linux/pci.h

@@ -2169,12 +2169,11 @@ static inline int pci_pcie_type(const struct pci_dev *dev)
  */
 static inline struct pci_dev *pcie_find_root_port(struct pci_dev *dev)
 {
-	struct pci_dev *bridge = pci_upstream_bridge(dev);
-
-	while (bridge) {
-		if (pci_pcie_type(bridge) == PCI_EXP_TYPE_ROOT_PORT)
-			return bridge;
-		bridge = pci_upstream_bridge(bridge);
+	while (dev) {
+		if (pci_is_pcie(dev) &&
+		    pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)
+			return dev;
+		dev = pci_upstream_bridge(dev);
 	}
 
 	return NULL;