ASoC: add Audio Graph Card2 driver

ASoC: add Audio Graph Card2 driver

We already have audio-graph-card which is Of-graph base of general
sound card driver.

It is supporting DPCM connection, but was forcibly expanded.
Thus, it is very difficult to add new features on it, for example
Multi CPU/Codec support, Codec2Codec support, etc.

This patch adds more flexible new Audio Graph Card2 driver for it.
audio-graph-card and audio-graph-card2 are similar, but don't have
full compatibility.

Audio Graph Card2 supports very generic connection, but some users
want to have its own settings, for example PLL settings, etc.
For such case, it has customizing support.
In users own driver, it can use Audio Graph Card2 parsing by using
audio_graph2_parse_of(), and doing its own customizing.

Because Audio Graph Card2 is still under experimental stage,
it will indicate such warning when probing, and the DT syntax
might be changed.

Link: https://lore.kernel.org/r/87k0xszlep.wl-kuninori.morimoto.gx@renesas.com
Link: https://lore.kernel.org/r/871r8u4s6q.wl-kuninori.morimoto.gx@renesas.com
Link: https://lore.kernel.org/r/87a6mhwyqn.wl-kuninori.morimoto.gx@renesas.com
Link: https://lore.kernel.org/r/87tuitusy4.wl-kuninori.morimoto.gx@renesas.com
Link: https://lore.kernel.org/r/87a6jn56x0.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/8735p6n8q1.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>