dt-bindings: arm: at91: add Kontron's new KSwitches

The Kontron KSwitch D10 MMT series ethernet switches features a LAN9668
SoC with either 8 copper ports or 6 copper port and two SFP cages.

Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20220210131817.484922-1-michael@walle.cc