dt-bindings: mtd: microchip,mchp23k256: convert to DT schema

Convert Microchip 23K256 SPI SRAM MTD binding to YAML format.
Changes during conversion:
- Remove "address-cells" and "size-cells" from properties and
  required sections as there is no child node for sram.

Signed-off-by: Akhila YS <akhilayalmati@gmail.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Author: Akhila-YS

Documentation/devicetree/bindings/mtd/microchip,mchp23k256.txt

@@ -0,0 +1,49 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mtd/microchip,mchp23k256.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Microchip 23K256 SPI SRAM
+
+maintainers:
+  - Richard Weinberger <richard@nod.at>
+
+description:
+  The Microchip 23K256 is a 256 Kbit (32 Kbyte) serial SRAM with an
+  SPI interface,supporting clock frequencies up to 20 MHz. It features
+  a 32-byte page size for writes and supports byte, page, and
+  sequential access modes.
+
+allOf:
+  - $ref: /schemas/spi/spi-peripheral-props.yaml#
+
+properties:
+  compatible:
+    enum:
+      - microchip,mchp23k256
+      - microchip,mchp23lcv1024
+
+  reg:
+    maxItems: 1
+
+required:
+  - reg
+  - compatible
+  - spi-max-frequency
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        sram@0 {
+            compatible = "microchip,mchp23k256";
+            reg = <0>;
+            spi-max-frequency = <20000000>;
+        };
+    };
+...