dt-bindings: dsp: fsl: Add SOF compatile string for i.MX8ULP

Add SOF compatile string "fsl,imx8ulp-dsp" for supporting DSP
device on i.MX8ULP platform.
Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Daniel Baluta <daniel.baluta@nxp.com>
Link: https://lore.kernel.org/r/1660787634-28550-1-git-send-email-shengjiu.wang@nxp.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/dsp/fsl,dsp.yaml

@@ -20,6 +20,7 @@ properties:
       - fsl,imx8qxp-dsp
       - fsl,imx8qm-dsp
       - fsl,imx8mp-dsp
+      - fsl,imx8ulp-dsp
       - fsl,imx8qxp-hifi4
       - fsl,imx8qm-hifi4
       - fsl,imx8mp-hifi4