dt-bindings: arm: bcm: Convert BCM23550 to YAML

Update the Broadcom BCM23550 SoC binding document for boards/SoCs to use
YAML. Verified with dt_binding_check and dtbs_check.
Acked-by: NScott Branden <scott.branden@broadcom.com>
Reviewed-by: NRob Herring <robh@kernel.org>
Signed-off-by: NFlorian Fainelli <f.fainelli@gmail.com>

Documentation/devicetree/bindings/arm/bcm/brcm,bcm23550.txt

-Broadcom BCM23550 device tree bindings
---------------------------------------
-
-This document describes the device tree bindings for boards with the BCM23550
-SoC.
-
-Required root node property:
-  - compatible: brcm,bcm23550
-
-Example:
-	/ {
-		model = "BCM23550 SoC";
-		compatible = "brcm,bcm23550";
-		[...]
-	}

Documentation/devicetree/bindings/arm/bcm/brcm,bcm23550.yaml

+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/arm/bcm/brcm,bcm23550.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Broadcom BCM23550 device tree bindings
+
+maintainers:
+  - Florian Fainelli <f.fainelli@gmail.com>
+
+properties:
+  $nodename:
+    const: '/'
+  compatible:
+    items:
+      - enum:
+        - brcm,bcm23550-sparrow
+      - const: brcm,bcm23550
+
+...