dt-bindings: arm: Convert Calxeda board/soc bindings to json-schema

Convert Calxeda SoC bindings to DT schema format using json-schema.

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: devicetree@vger.kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/arm/calxeda.txt

-Calxeda Platforms Device Tree Bindings
------------------------------------------------
-
-Boards with Calxeda Cortex-A9 based ECX-1000 (Highbank) SOC shall have the
-following properties.
-
-Required root node properties:
-    - compatible = "calxeda,highbank";
-
-
-Boards with Calxeda Cortex-A15 based ECX-2000 SOC shall have the following
-properties.
-
-Required root node properties:
-    - compatible = "calxeda,ecx-2000";

Documentation/devicetree/bindings/arm/calxeda.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/arm/calxeda.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Calxeda Platforms Device Tree Bindings
+
+maintainers:
+  - Rob Herring <robh@kernel.org>
+description: |+
+  Bindings for boards with Calxeda Cortex-A9 based ECX-1000 (Highbank) SOC
+  or Cortex-A15 based ECX-2000 SOCs
+
+properties:
+  $nodename:
+    const: '/'
+  compatible:
+    items:
+      - enum:
+          - calxeda,highbank
+          - calxeda,ecx-2000