ASoC: dt-bindings: Add documentation for TI j721e EVM (CPB and IVI)

The audio support on the Common Processor Board board is using
pcm3168a codec connected to McASP10 serializers in parallel setup.

The Infotainment board plugs into the Common Processor Board, the support
of the extension board is extending the CPB audio support by adding
the two codecs on the expansion board.

The audio support on the Infotainment Expansion Board consists of McASP0
connected to two pcm3168a codecs with dedicated set of serializers to each.
The SCKI for pcm3168a is sourced from j721e AUDIO_REFCLK0 pin.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20200630125843.11561-3-peter.ujfalusi@ti.com


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