dt-bindings: cros-ec: Remove google,cros-kbd-led-backlight

After applying 4c03a44e2668 ("arm64: dts: mediatek: mt8195-cherry: Remove
keyboard-backlight node"), there are no users for using the OF match.
Instead, the device is added via drivers/mfd/cros_ec_dev.c by
970c3a6b7aa3 ("mfd: cros_ec: Register keyboard backlight subdevice").

Remove the DT bindings.

Acked-by: Rob Herring (Arm) <[e-mail]>
Acked-by: Lee Jones <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Tzung-Bi Shih <[e-mail]>

Documentation/devicetree/bindings/chrome/google,cros-kbd-led-backlight.yaml

···
-# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
-%YAML 1.2
----
-$id: http://devicetree.org/schemas/chrome/google,cros-kbd-led-backlight.yaml#
-$schema: http://devicetree.org/meta-schemas/core.yaml#
-
-title: ChromeOS keyboard backlight LED driver.
-
-maintainers:
-  - Tzung-Bi Shih <[e-mail]>
-
-properties:
-  compatible:
-    const: google,cros-kbd-led-backlight
-
-required:
-  - compatible
-
-additionalProperties: false
-
-examples:
-  - |
-    spi {
-      #address-cells = <1>;
-      #size-cells = <0>;
-
-      cros_ec: ec@0 {
-        compatible = "google,cros-ec-spi";
-        reg = <0>;
-        interrupts = <15 0>;
-
-        kbd-led-backlight {
-          compatible = "google,cros-kbd-led-backlight";
-        };
-      };
-    };

Documentation/devicetree/bindings/mfd/google,cros-ec.yaml

···
   pwm:
     $ref: /schemas/pwm/google,cros-ec-pwm.yaml#
 
-  kbd-led-backlight:
-    $ref: /schemas/chrome/google,cros-kbd-led-backlight.yaml#
-
   keyboard-controller:
     $ref: /schemas/input/google,cros-ec-keyb.yaml#