dt-bindings: rtc: pxa-rtc: convert to dtschema

Convert existing binding to dtschema to support validation.

The missing 'reg' and 'interrupts' properties have been added, taking
the 2 supported interrupts into account to fix the example.
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://lore.kernel.org/r/20240413-rtc_dtschema-v3-3-eff368bcc471@gmail.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Documentation/devicetree/bindings/rtc/marvell,pxa-rtc.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/rtc/marvell,pxa-rtc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: PXA Real Time Clock
+
+maintainers:
+  - Javier Carrasco <javier.carrasco.cruz@gmail.com>
+
+allOf:
+  - $ref: rtc.yaml#
+
+properties:
+  compatible:
+    const: marvell,pxa-rtc
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    items:
+      - description: 1 Hz
+      - description: Alarm
+
+required:
+  - compatible
+  - reg
+  - interrupts
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    rtc@40900000 {
+        compatible = "marvell,pxa-rtc";
+        reg = <0x40900000 0x3c>;
+        interrupts = <30>, <31>;
+    };

Documentation/devicetree/bindings/rtc/pxa-rtc.txt

-* PXA RTC
-
-PXA specific RTC driver.
-
-Required properties:
-- compatible : Should be "marvell,pxa-rtc"
-
-Examples:
-
-rtc@40900000 {
-	compatible = "marvell,pxa-rtc";
-	reg = <0x40900000 0x3c>;
-	interrupts = <30 31>;
-};