net: Add sysfs file for port number

Add a sysfs file to enable user space to query the device
port number used by a netdevice instance. This is needed for
devices that have multiple ports on the same PCI function.

Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -1279,6 +1279,10 @@ struct net_device {
 						 * that share the same link
 						 * layer address
 						 */
+	unsigned short          dev_port;	/* Used to differentiate
+						 * devices that share the same
+						 * function
+						 */
 	spinlock_t		addr_list_lock;
 	struct netdev_hw_addr_list	uc;	/* Unicast mac addresses */
 	struct netdev_hw_addr_list	mc;	/* Multicast mac addresses */