ASoC: max98396: Implement DSP speaker monitor

Allow the selection of the TDM slot that is used to send back speaker
monitor data. The DT property adi,spkfb-slot-no can be used to configure
this setting which defaults to 2.

Signed-off-by: Daniel Mack <daniel@zonque.org>
Link: https://lore.kernel.org/r/20220624104712.1934484-8-daniel@zonque.org


Signed-off-by: Mark Brown <broonie@kernel.org>