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

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

Cc: Anders Berg <anders.berg@lsi.com>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/arm/axxia.txt

-Axxia AXM55xx device tree bindings
-
-Boards using the AXM55xx SoC need to have the following properties:
-
-Required root node property:
-
-  - compatible = "lsi,axm5516"
-
-Boards:
-
-  LSI AXM5516 Validation board (Amarillo)
-	compatible = "lsi,axm5516-amarillo", "lsi,axm5516"

Documentation/devicetree/bindings/arm/axxia.yaml

+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/arm/axxia.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Axxia AXM55xx device tree bindings
+
+maintainers:
+  - Anders Berg <anders.berg@lsi.com>
+
+properties:
+  compatible:
+    description: LSI AXM5516 Validation board (Amarillo)
+    items:
+      - const: lsi,axm5516-amarillo
+      - const: lsi,axm5516
+
+...