ASoC: dt-bindings: renesas,rsnd: add missing playback/capture

ASoC: dt-bindings: renesas,rsnd: add missing playback/capture

renesas,rsnd.yaml is possible to use ports/port/endpoint if it is using
Audio Graph Card/Card2 for sound. The schema is defined under
audio-graph-port.yaml.

rsnd driver needs "playback/capture" property under endpoint, but it is not
defined in audio-graph-port.yaml. This patch adds missing "playback/capture"
properties under endpoint.

Without this patch, we will get below warning

${LINUX}/arch/arm64/boot/dts/renesas/r8a77950-salvator-x.dtb: sound@ec500000: ports:port@0:endpoint: Unevaluated properties are not allowed ('playback', 'capture' were unexpected)
	From schema: ${LINUX}/Documentation/devicetree/bindings/sound/renesas,rsnd.yaml

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87h6wh7rfj.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>