Audio Graph endpoint is possible to have clocks, and system-clock-xxx,
but these are missing on audio-graph-port.yaml.
These have been already defined on simple-card.yaml.

This patch re-use these.  We will get below warning without this patch.

${LINUX}/arch/arm64/boot/dts/renesas/r8a77950-ulcb-kf.dtb: audio-codec@44: ports:port@0:endpoint: Unevaluated properties are not allowed ('clocks' was unexpected)
	From schema: ${LINUX}/Documentation/devicetree/bindings/sound/ti,pcm3168a.yaml

Link: https://lore.kernel.org/r/87pmcmpyml.wl-kuninori.morimoto.gx@renesas.comSigned-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87mt697rgg.wl-kuninori.morimoto.gx@renesas.comSigned-off-by: Mark Brown <broonie@kernel.org>