ASoC: audio-graph-card2: add support for aux devices

Add device tree property to define auxiliary devices to be added to
Audio Graph Card which is already supported on Simle Card.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://msgid.link/r/878qz4ry81.wl-kuninori.morimoto.gx@renesas.com


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