dt-bindings: ARM: Mediatek: Fix ethsys documentation

The ethsys registers a reset controller, so we need to specify a
reset cell. This patch fixes the documentation.
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>

Documentation/devicetree/bindings/arm/mediatek/mediatek,ethsys.txt

@@ -20,4 +20,5 @@ ethsys: clock-controller@1b000000 {
 	compatible = "mediatek,mt2701-ethsys", "syscon";
 	reg = <0 0x1b000000 0 0x1000>;
 	#clock-cells = <1>;
+	#reset-cells = <1>;
 };