net: dsa: microchip: enable ETS support for KSZ989X variants

I tested ETS support on KSZ9893, so it should work other KSZ989X
variants too, which was till not listed as support.

With this change we now officially not support only ksz8 family of
chips.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Acked-by: Arun Ramadoss <arun.ramadoss@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>