ASoC: dt-bindings: Update example for enabling USB offload on SM8250

Add an example on enabling of USB offload for the Q6DSP.  The routing can
be done by the mixer, which can pass the multimedia stream to the USB
backend.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
Acked-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20250409194804.3773260-22-quic_wcheng@quicinc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

@@ -190,4 +190,19 @@ examples:
                 sound-dai = <&vamacro 0>;
             };
         };
+
+        usb-dai-link {
+            link-name = "USB Playback";
+            cpu {
+                sound-dai = <&q6afedai USB_RX>;
+            };
+
+            codec {
+                sound-dai = <&usbdai USB_RX>;
+            };
+
+            platform {
+                sound-dai = <&q6routing>;
+            };
+        };
     };