arm64: dts: verdin-imx8mm: fix dahlia audio playback

Set optional `simple-audio-card,mclk-fs` parameter to ensure a proper
clock to the wm8904 audio codec. Without this change with an audio
stream rate of 44.1 kHz the playback is completely distorted.

Fixes: 6a57f224 ("arm64: dts: freescale: add initial support for verdin imx8m mini")
Signed-off-by: Emanuele Ghidoli <emanuele.ghidoli@toradex.com>
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>