ASoC: dt-bindings: qcom,sm8250: Add Fairphone 4 sound card

Document the bindings for the sound card on Fairphone 4 which uses the
older non-audioreach audio architecture.

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Luca Weiss <luca.weiss@fairphone.com>
Link: https://patch.msgid.link/20250723-fp4-usb-audio-offload-v3-2-6be84ed4fc39@fairphone.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: lweiss-fairphone

Documentation/devicetree/bindings/sound/qcom,sm8250.yaml

@@ -28,6 +28,7 @@ properties:
               - qcom,sm8750-sndcard
           - const: qcom,sm8450-sndcard
       - enum:
+          - fairphone,fp4-sndcard
           - fairphone,fp5-sndcard
           - qcom,apq8096-sndcard
           - qcom,qcm6490-idp-sndcard