ASoC: dt-bindings: audio-graph-port: add definitions/ports

ASoC: dt-bindings: audio-graph-port: add definitions/ports

Audio Graph user needs "ports" not only "port".
This patch adds standard "ports" as definitions to use it easily.

If user needs standard "ports", it can use

   ports:
     $ref: audio-graph-port.yaml#/definitions/ports

If user want to use custom ports, it can re-use
audio-graph-port.yaml#/definitions/port-base"
audio-graph-port.yaml#/definitions/endpoint-base"

Link: https://lore.kernel.org/r/87sfhipynv.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87pmb57rh2.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>