arm64: dts: imx8mm-evk: support more sample rates for wm8524 card

arm64: dts: imx8mm-evk: support more sample rates for wm8524 card

The wm8524 codec is connected to the SAI interface. There are two audio
plls on i.MX8MM, one pll can be the clock source of 44kHz series rates,
another pll can be clock source of 48kHz series rates.

Previously it only supported 48kHz series rates, with this change the
supported rates will include 44kHz series rates, from 8kHz to 192kHz.

As commit 17cc308b1833 ("ASoC: wm8524: enable constraints when sysclk is
configured.") make wm8524 release the constraint when codec's sysclk is
not configured, so configure the cpu dai's sysclk to support more rates
with the 'clocks' property removed.

Add mclk-fs property for the sysclk ratio, which is required by
calculating the sysclk, 256 is a common ratio for audio.

'system-clock-direction-out' is a required property after
commit 5725bce709db ("ASoC: simple-card-utils: Unify clock direction by
clk_direction") to specify the clock direction.

Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>