Add find_pci_netdev()

src/include/gpxe/netdevice.h

 extern void unregister_netdev ( struct net_device *netdev );
 extern void free_netdev ( struct net_device *netdev );
 struct net_device * find_netdev ( const char *name );
+struct net_device * find_pci_netdev ( unsigned int busdevfn );
+
 extern int net_tx ( struct pk_buff *pkb, struct net_device *netdev,
 		    struct net_protocol *net_protocol, const void *ll_dest );
 extern int net_rx ( struct pk_buff *pkb, struct net_device *netdev,

src/net/netdevice.c

 	return NULL;
 }
 
+/**
+ * Get network device by PCI bus:dev.fn address
+ *
+ * @v busdevfn		PCI bus:dev.fn address
+ * @ret netdev		Network device, or NULL
+ */
+struct net_device * find_pci_netdev ( unsigned int busdevfn ) {
+	struct net_device *netdev;
+
+	list_for_each_entry ( netdev, &net_devices, list ) {
+		if ( ( netdev->dev->desc.bus_type == BUS_TYPE_PCI ) &&
+		     ( netdev->dev->desc.pci.busdevfn == busdevfn ) )
+			return netdev;
+	}
+
+	return NULL;	
+}
+
 /**
  * Transmit network-layer packet
  *