ASoC: simple_card_utils: share common priv for simple-card/audio-graph

Historically, simple-card/simple-scu-card/audio-graph/audio-graph-scu
are similar but different generic sound card.
simple-scu-card which was for DPCM was merged into simple-card, and
audio-graph-scu which was for DPCM was merged into audio-graph.
simple-card is for non OF graph sound card, and
audio-graph is for     OF graph sound card.
And, small detail difference (= function parameter, naming, etc)
between simple-card/audio-graph has been unified.

So today, the difference between simple-card/audio-graph are
just using OF graph style, or not.
In other words, there should no difference other than OF graph sytle.
simple-card/audio-graph are using own priv today , but we can merge it.
This patch merge it at simple_card_utils.

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