arm64: dts: imx8mm-evk: Enable audio codec wm8524

i.MX8MM has one wm8524 audio codec connected with
SAI3 digital audio interface.

This patch uses simple-card machine driver in order
to enable wm8524 codec.

We need to set:
	* SAI3 pinctrl configuration
	* codec reset gpio pinctrl configuration
	* clock hierarchy
	* codec node
	* simple-card configuration

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