dt-bindings: rtc: convert MT2717 RTC to the json-schema

This helps validating DTS files. Introduced changes:
1. Reworded title
2. Dropper redundant properties descriptions
3. Added required #include and adjusted "reg" in example

Signed-off-by: Rafał Miłecki <[e-mail]>
Reviewed-by: Matthias Brugger <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexandre Belloni <[e-mail]>

Documentation/devicetree/bindings/rtc/mediatek,mt2712-rtc.yaml

···
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/rtc/mediatek,mt2712-rtc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: MediaTek MT2712 on-SoC RTC
+
+allOf:
+  - $ref: rtc.yaml#
+
+maintainers:
+  - Ran Bi <[e-mail]>
+
+properties:
+  compatible:
+    const: mediatek,mt2712-rtc
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+required:
+  - reg
+  - interrupts
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+
+    rtc@10011000 {
+        compatible = "mediatek,mt2712-rtc";
+        reg = <0x10011000 0x1000>;
+        interrupts = <GIC_SPI 239 IRQ_TYPE_LEVEL_LOW>;
+    };

Documentation/devicetree/bindings/rtc/rtc-mt2712.txt

···
-Device-Tree bindings for MediaTek SoC based RTC
-
-Required properties:
-- compatible	    : Should be "mediatek,mt2712-rtc" : for MT2712 SoC
-- reg 		    : Specifies base physical address and size of the registers;
-- interrupts	    : Should contain the interrupt for RTC alarm;
-
-Example:
-
-rtc: rtc@10011000 {
-	compatible = "mediatek,mt2712-rtc";
-	reg = <0 0x10011000 0 0x1000>;
-	interrupts = <GIC_SPI 239 IRQ_TYPE_LEVEL_LOW>;
-};