dt-bindings: power: reset: gpio-poweroff: Add priority property

Add the priority property to the gpio-poweroff bindings description.

Signed-off-by: Stefan Eichenberger <[e-mail]>
Signed-off-by: Francesco Dolcini <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Sebastian Reichel <[e-mail]>

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

···
   Finally the operating system assumes the power off failed if
   the system is still running after waiting some time (timeout-ms).
 
+allOf:
+  - $ref: restart-handler.yaml#
+
 properties:
   compatible:
     const: gpio-poweroff
···
   inactive-delay-ms:
     default: 100
     description: Delay to wait after driving gpio inactive
+
+  priority:
+    default: 0
 
   timeout-ms:
     default: 3000