macvlan: Fix memleak on device removal/crash on module removal

As noticed by Ben Greear, macvlan crashes the kernel when unloading the
module. The reason is that it tries to clean up the macvlan_port pointer
on the macvlan device itself instead of the underlying device. A non-NULL
pointer is taken as indication that the macvlan_handle_frame_hook is
valid, when receiving the next packet on the underlying device it tries
to call the NULL hook and crashes.

Clean up the macvlan_port on the correct device to fix this.

Signed-off-by; Patrick McHardy <[e-mail]>
Tested-by: Ben Greear <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/macvlan.c

···
 	unregister_netdevice(dev);
 
 	if (list_empty(&port->vlans))
-		macvlan_port_destroy(dev);
+		macvlan_port_destroy(port->dev);
 }
 
 static struct rtnl_link_ops macvlan_link_ops __read_mostly = {