dt-bindings: arm: bcm: Convert BCM21664 to YAML

Update the Broadcom BCM21664 SoC binding document for boards/SoCs to use
YAML. Verified with dt_binding_check and dtbs_check.

Acked-by: Scott Branden <scott.branden@broadcom.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

Documentation/devicetree/bindings/arm/bcm/brcm,bcm21664.txt

@@ -1,15 +0,0 @@
-Broadcom BCM21664 device tree bindings
---------------------------------------
-
-This document describes the device tree bindings for boards with the BCM21664
-SoC.
-
-Required root node property:
-  - compatible: brcm,bcm21664
-
-Example:
-	/ {
-		model = "BCM21664 SoC";
-		compatible = "brcm,bcm21664";
-		[...]
-	}

Documentation/devicetree/bindings/arm/bcm/brcm,bcm21664.yaml

@@ -0,0 +1,21 @@
+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/arm/bcm/brcm,bcm21664.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Broadcom BCM21664 device tree bindings
+
+maintainers:
+  - Florian Fainelli <f.fainelli@gmail.com>
+
+properties:
+  $nodename:
+    const: '/'
+  compatible:
+    items:
+      - enum:
+        - brcm,bcm21664-garnet
+      - const: brcm,bcm21664
+
+...