arm64: dts: imx8mq-evk: Enable audio codec wm8524

The main Audio DAC used on the EVK board is wm8524
The EVK provides the MCLK to wm8524.

Digital interface is SAI2 which includes three signals:
SYNC_CLK, BCLK and DACDAT.

This patch sets:
        * SAI2 pinctrl configuration
        * clock hierarchy
        * wm8524 codec

Then uses simple-card machine driver to connect them
into a sound card.

Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>