Fixes for the audio setup on the rk3588-nanopc-t6

Merge series from Heiko Stuebner <heiko@sntech.de>:

The Nanopc-T6 board does contain some devicetree errors, that came to
light with recent changes to the board.

Documentation/devicetree/bindings/sound/realtek,rt5616.yaml

@@ -30,6 +30,18 @@ properties:
   reg:
     maxItems: 1
 
+  clocks:
+    items:
+      - description: Master clock to the CODEC
+
+  clock-names:
+    items:
+      - const: mclk
+
+  port:
+    $ref: audio-graph-port.yaml#
+    unevaluatedProperties: false
+
 required:
   - compatible
   - reg