ASoC: add DT bindings for Microchip S/PDIF TX Controller

This patch adds DT bindings for the new Microchip S/PDIF TX Controller
embedded inside sama7g5 SoCs.

Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200909145348.367033-1-codrin.ciubotariu@microchip.com


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