ASoC: bindings: fsl-asoc-card: add compatible string for nau8822 codec

The nau8822 codec is used on an imx6sx EVB.
Signed-off-by: Hui Wang <hui.wang@canonical.com>
Link: https://lore.kernel.org/r/Message-Id: <20220616040046.103524-2-hui.wang@canonical.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/fsl-asoc-card.txt

@@ -46,6 +46,8 @@ The compatible list for this generic sound card currently:
 
  "fsl,imx-audio-wm8958"
 
+ "fsl,imx-audio-nau8822"
+
 Required properties:
 
   - compatible		: Contains one of entries in the compatible list.