arm64: dts: imx8mp: Enable SAI audio on Data Modul i.MX8M Plus eDM SBC

arm64: dts: imx8mp: Enable SAI audio on Data Modul i.MX8M Plus eDM SBC

Add SAI I2S and audio bindings to Data Modul i.MX8M Plus eDM SBC.

The SGTL5000 is attached to SAI3, however the SGTL5000 codec MCLK
must be supplied even if the SAI3 is not in use and is controlled
separately by the codec. The MCLK is also used to drive the codec
I2C block, so without MCLK, I2C access to the codec would not be
possible.

To provide such flexible MCLK control, use PWM4 with period 1 and
duty cycle 50% as 12 MHz clock source, as there is no direct way
to route MX8MP CCM clock to the MCLK pin. Use codec as bitclock
and frame clock master, so that the SGTL5000 PLL can be used to
generate derived clock.

Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>