ASoC need to use card->mutex with _INIT or _RUNTIME,
but there is no helper function for it.

This patch adds its helper function and use it.

Because people might misunderstand that _init() is mutex initialization,
this patch renames _INIT to _ROOT and adds new
snd_soc_card_mutex_lock_root() for it.
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87a5zlx3tw.wl-kuninori.morimoto.gx@renesas.comSigned-off-by: Mark Brown <broonie@kernel.org>