MLK-26155 arm64: dts: imx8mp-evk-sof-pdm: Fix PDM CLK rate

commit  faa38ac84e7d93ff0c60e4dc32456768a34c9fb6 from
https://github.com/nxp-imx/linux-imx

 lf-6.1.y

We don't have a way yet to set PDM clock from SOF firmware so
we need to set it from Linux side.

SOF PDM MICIFIL driver expects for PDM CLK rate to be 24576000
so set it here in order to fix PDM noise.

Reviewed-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Xiaolei Wang <xiaolei.wang@windriver.com>