ASoC: dt-bindings: aiu: spdif-dit: add missing sound-name-prefix property

This is used in meson-gx. Add the property to the binding.
This fixes the dtschema warning:
audio-controller@5400: 'sound-name-prefix' does not match any of the
regexes: 'pinctrl-[0-9]+'

Signed-off-by: Alexander Stein <alexander.stein@mailbox.org>
Link: https://lore.kernel.org/r/20211223122434.39378-4-alexander.stein@mailbox.org
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/amlogic,aiu.yaml

@@ -9,6 +9,9 @@ title: Amlogic AIU audio output controller
 maintainers:
   - Jerome Brunet <jbrunet@baylibre.com>
 
+allOf:
+  - $ref: name-prefix.yaml#
+
 properties:
   $nodename:
     pattern: "^audio-controller@.*"
@@ -65,6 +68,8 @@ properties:
   resets:
     maxItems: 1
 
+  sound-name-prefix: true
+
 required:
   - "#sound-dai-cells"
   - compatible