arm64: dts: imx8mn-bsh-smm-s2pro: Add tlv320aic31xx audio card node

BSH SystemMaster (SMM) S2 PRO board comes with an audio card based on
tlv320aic31xx family codec.

The audio card exposes two playback devices, one of them using the EASRC
(Enhanced Asynchronous Sample Rate Converter) module. Note that this
would require SDMA and EASRC firmware in order to work.

Signed-off-by: Ariel D'Alessandro <ariel.dalessandro@collabora.com>
Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>