ASoC: ak4613: add missing mutex_lock()

We need to use mutex_lock() for priv->cnt / priv->iface,
but we are missing it at ak4613_dai_startup().
This patch adds missing mutex_lock() for it.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87fsmsp9m7.wl-kuninori.morimoto.gx@renesas.com


Signed-off-by: Mark Brown <broonie@kernel.org>