ASoC: audio-graph-scu-card: remove audio-graph-scu-card

It is already merged into audio-graph-card.
audio-graph-scu-card is no longer needed.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>