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/iqs626a.yaml

@@ -449,6 +449,7 @@ patternProperties:
     patternProperties:
       "^event-(prox|touch|deep)(-alt)?$":
         type: object
+        $ref: input.yaml#
         description:
           Represents a proximity, touch or deep-touch event reported by the
           channel in response to a decrease in counts. Node names suffixed with
@@ -487,9 +488,7 @@ patternProperties:
               Specifies the hysteresis for the event (touch and deep-touch
               events only).
 
-          linux,code:
-            $ref: /schemas/types.yaml#/definitions/uint32
-            description: Numeric key or switch code associated with the event.
+          linux,code: true
 
           linux,input-type:
             $ref: /schemas/types.yaml#/definitions/uint32