Current soc_pcm_open() calls snd_soc_dai_startup() under loop.
Thus, it needs to care about started/not-yet-started codec DAI.

But, if soc-dai.c is handling it, soc-pcm.c don't need to care
about it.
This patch adds started flag to soc-dai.h, and simplify soc-pcm.c.
This is one of prepare for cleanup soc-pcm-open()
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/875zgfcey5.wl-kuninori.morimoto.gx@renesas.comSigned-off-by: Mark Brown <broonie@kernel.org>