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>