Add support for offloading ets qdisc to sparx5 switch.

The ets qdisc makes it possible to configure a mix og strict and
bandwidth-sharing bands. The ets qdisc must be attached as a root qdisc.
Signed-off-by: NDaniel Machon <daniel.machon@microchip.com>
Signed-off-by: NSteen Hegelund <steen.hegelund@microchip.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>