dt-bindings: input: Centralize 'linux,code' definition

Multiple bindings use 'linux,code', but there is not a central
definition and type. Add 'linux,code' to input.yaml and update all the
users to use it.

Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Samuel Holland <samuel@sholland.org>
Acked-by: Jeff LaBundy <jeff@labundy.com>
Acked-by: Artur Rojek <contact@artur-rojek.eu>
Link: https://lore.kernel.org/r/20220608211207.2058487-3-robh@kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Documentation/devicetree/bindings/input/max77650-onkey.yaml

@@ -16,15 +16,15 @@ description: |
   The onkey controller is represented as a sub-node of the PMIC node on
   the device tree.
 
+allOf:
+  - $ref: input.yaml#
+
 properties:
   compatible:
     const: maxim,max77650-onkey
 
   linux,code:
-    $ref: /schemas/types.yaml#/definitions/uint32
-    description:
-      The key-code to be reported when the key is pressed. Defaults
-      to KEY_POWER.
+    default: 116  # KEY_POWER
 
   maxim,onkey-slide:
     $ref: /schemas/types.yaml#/definitions/flag