ASoC: dt-bindings: fsl_spdif: Add new compatible string for i.MX8QM

Add new compatible string "fsl,imx8qm-spdif" for supporting spdif
module on i.MX8QM.
Signed-off-by: NShengjiu Wang <shengjiu.wang@nxp.com>
Acked-by: NRob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1602739728-4433-1-git-send-email-shengjiu.wang@nxp.comSigned-off-by: NMark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/fsl,spdif.yaml

@@ -20,6 +20,7 @@ properties:
       - fsl,imx35-spdif
       - fsl,vf610-spdif
       - fsl,imx6sx-spdif
+      - fsl,imx8qm-spdif
 
   reg:
     maxItems: 1