ASoC: soc-dapm: add snd_soc_dapm_to_card()

ASoC: soc-dapm: add snd_soc_dapm_to_card()

Because struct snd_soc_dapm_context is soc-dapm framework specific, user
driver don't need to access its member directly, we would like to hide
them. struct snd_soc_dapm_context will be removed from header in the
future.

Some drivers need to get card from dapm (which will be removed).
We need such function. Add it.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://patch.msgid.link/87bjnqx06v.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>