ASoC: dt-bindings: audio-graph-port: use definitions for port/endpoint

Audio Graph base driver might need to add its own properties.
In such case, having definitions for port/endpoint is easy to handle it.
This patch adds definitions for port/endpoint.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87r0vl7rj4.wl-kuninori.morimoto.gx@renesas.com


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