dts: gpio: it8xxx2: Remove unused property

Property of port-is-output is not used anymore, so let's remove it.

Signed-off-by: Dino Li <Dino.Li@ite.com.tw>

Author: Dino-Li

dts/bindings/gpio/ite,it8xxx2-gpio.yaml

@@ -8,10 +8,6 @@ compatible: "ite,it8xxx2-gpio"
 include: [gpio-controller.yaml, base.yaml]
 
 properties:
-    port-is-output:
-      type: boolean
-      description: Indicates if the port is an output port
-
     reg:
       required: true