PCI: enhance pci_ari_enabled()

Change parameter of pci_ari_enabled() from 'pci_dev' to 'pci_bus'.

ARI forwarding on the bridge mostly concerns the subordinate devices
rather than the bridge itself. So this change will make the function
easier to use.
Signed-off-by: Yu Zhao <yu.zhao@intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/pci.h

@@ -165,13 +165,13 @@ struct pci_slot_attribute {
 extern void pci_enable_ari(struct pci_dev *dev);
 /**
  * pci_ari_enabled - query ARI forwarding status
- * @dev: the PCI device
+ * @bus: the PCI bus
  *
  * Returns 1 if ARI forwarding is enabled, or 0 if not enabled;
  */
-static inline int pci_ari_enabled(struct pci_dev *dev)
+static inline int pci_ari_enabled(struct pci_bus *bus)
 {
-	return dev->ari_enabled;
+	return bus->self && bus->self->ari_enabled;
 }
 
 #endif /* DRIVERS_PCI_H */