dt-bindings: input: pwm-beeper: convert to dt schema

Convert the binding doc to dt schema, and also fixed the
example from fixed-regulator to regulator-fixed.
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230407075259.1593739-1-peng.fan@oss.nxp.comSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Documentation/devicetree/bindings/input/pwm-beeper.txt

-* PWM beeper device tree bindings
-
-Registers a PWM device as beeper.
-
-Required properties:
-- compatible: should be "pwm-beeper"
-- pwms: phandle to the physical PWM device
-
-Optional properties:
-- amp-supply: phandle to a regulator that acts as an amplifier for the beeper
-- beeper-hz:  bell frequency in Hz
-
-Example:
-
-beeper_amp: amplifier {
-	compatible = "fixed-regulator";
-	gpios = <&gpio0 1 GPIO_ACTIVE_HIGH>;
-};
-
-beeper {
-	compatible = "pwm-beeper";
-	pwms = <&pwm0>;
-	amp-supply = <&beeper_amp>;
-};

Documentation/devicetree/bindings/input/pwm-beeper.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/input/pwm-beeper.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: PWM beeper
+
+maintainers:
+  - Sascha Hauer <s.hauer@pengutronix.de>
+
+properties:
+  compatible:
+    const: pwm-beeper
+
+  pwms:
+    maxItems: 1
+
+  amp-supply:
+    description: an amplifier for the beeper
+
+  beeper-hz:
+    description: bell frequency in Hz
+    minimum: 10
+    maximum: 10000
+
+required:
+  - compatible
+  - pwms
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    beeper {
+        compatible = "pwm-beeper";
+        pwms = <&pwm0>;
+        amp-supply = <&beeper_amp>;
+        beeper-hz = <1000>;
+    };