linux-imx

ASoC: add audio-graph-card document

"Audio Graph Card" = "Simple Card" + "OF-graph"

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>