dt-bindings: power: reset: gpio-poweroff: Add 'timeout-ms' property

Add 'timeout-ms' property to support boards where the 3s timeout that the
current driver defaults to is too short.

Signed-off-by: Moritz Fischer <mdf@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>

Documentation/devicetree/bindings/power/reset/gpio-poweroff.txt

@@ -27,10 +27,13 @@ Optional properties:
   it to an output when the power-off handler is called. If this optional
   property is not specified, the GPIO is initialized as an output in its
   inactive state.
+- timeout-ms: Time to wait before asserting a WARN_ON(1). If nothing is
+              specified, 3000 ms is used.
 
 Examples:
 
 gpio-poweroff {
 	compatible = "gpio-poweroff";
 	gpios = <&gpio 4 0>;
+	timeout-ms = <3000>;
 };