ASoC: dt-bindings: fsl,spdif: Add compatible string for imx8ulp

Add compatible string for imx8ulp, which supports spdif module

Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1622613849-10271-1-git-send-email-shengjiu.wang@nxp.com


Signed-off-by: Mark Brown <broonie@kernel.org>