ASoC: audio-graph-card2-custom-sample.dtsi: remove DT warning

Current audio-graph-card2-custom-sample.dtsi is missing
address-cells / size-cells / reg. Thus it get too many DT warnings.
This patch solved it.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87a5x5qw3d.wl-kuninori.morimoto.gx@renesas.com


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