ASoC: simple-card-utils: add asoc_graph_is_ports0()

audio-graph-card2 will support DPCM/Multi/Codec2Codec,
and these will use almost same DT settings which uses
ports0 and ports1.
This patch adds asoc_graph_is_ports0() which checks
port is under port0 or not.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/875yu2n8ra.wl-kuninori.morimoto.gx@renesas.com


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