ASoC: codecs: ak*: merge .digital_mute() into .mute_stream()

ASoC: codecs: ak*: merge .digital_mute() into .mute_stream()

snd_soc_dai_digital_mute() is internally using both
mute_stream() (1) or digital_mute() (2), but the difference between
these 2 are only handling direction.
We can merge digital_mute() into mute_stream

	int snd_soc_dai_digital_mute(xxx, int direction)
	{
		...
		else if (dai->driver->ops->mute_stream)
(1)			return dai->driver->ops->mute_stream(xxx, direction);
		else if (direction == SNDRV_PCM_STREAM_PLAYBACK &&
			 dai->driver->ops->digital_mute)
(2)			return dai->driver->ops->digital_mute(xxx);
		...
	}

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Reviewed-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/87pn95wiwa.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>