ASoC: dt-bindings: Document audio OF graph dai-tdm-slot-num dai-tdm-slot-width props

Document dai-tdm-slot-num and dai-tdm-slot-width props as those are
parsed by simple graph card and may therefore appear in audio OF graph
node.

Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220927185359.294322-1-marex@denx.de


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