ASoC: dt-bindings: nau8822: add nuvoton,spk-btl property to dtschema

Add nuvoton,spk-btl to configure the two loudspeaker outputs
as Bridge Tied Load

Cc: David Lin <CTLIN0@nuvoton.com>
Signed-off-by: Emanuele Ghidoli <emanuele.ghidoli@toradex.com>
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230104195350.149300-1-francesco@dolcini.itSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/nuvoton,nau8822.yaml

@@ -21,6 +21,12 @@ properties:
   reg:
     maxItems: 1
 
+  nuvoton,spk-btl:
+    description:
+      If set, configure the two loudspeaker outputs as a Bridge Tied Load output
+      to drive a high power external loudspeaker.
+    $ref: /schemas/types.yaml#/definitions/flag
+
 required:
   - compatible
   - reg