dt-bindings: net: dsa: qca8k: document reset-gpios property

This patch documents the qca8k's reset-gpios property that
can be used if the QCA8337N ends up in a bad state during
reset.

Signed-off-by: Christian Lamparter <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

Documentation/devicetree/bindings/net/dsa/qca8k.txt

···
 - #size-cells: must be 0
 - #address-cells: must be 1
 
+Optional properties:
+
+- reset-gpios: GPIO to be used to reset the whole device
+
 Subnodes:
 
 The integrated switch subnode should be specified according to the binding
···
 			#address-cells = <1>;
 			#size-cells = <0>;
 
+			reset-gpios = <&gpio 42 GPIO_ACTIVE_LOW>;
 			reg = <0x10>;
 
 			ports {
···
 			#address-cells = <1>;
 			#size-cells = <0>;
 
+			reset-gpios = <&gpio 42 GPIO_ACTIVE_LOW>;
 			reg = <0x10>;
 
 			ports {