ASoC: audio-graph-card: use new of_graph functions

Now we can use new port related functions for port parsing. Use it.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Acked-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/87fromb5sr.wl-kuninori.morimoto.gx@renesas.com


Signed-off-by: Rob Herring (Arm) <robh@kernel.org>