ASoC: bindings: fsl-asoc-card: Add compatible string for wm8524

In order to support wm8524 codec with fsl-asoc-card machine
driver, add compatible string "fsl,imx-audio-wm8524".

Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Acked-by: Nicolin Chen <nicoleotsuka@gmail.com>
Link: https://lore.kernel.org/r/1592895167-30483-2-git-send-email-shengjiu.wang@nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>