ASoC: rsnd: call snd_soc_disconnect_sync() when remove

Renesas R-Car sound driver should be stopped if unbinded during
playbacking/capturing. Otherwise clock open/close counter mismatch
happen.

One note is that we can't skip from remove function (= return -Exxx)
in such case if user used unbind. Because unbind function doesn't
check return value from each driver's remove function.
This means we must to stop and remove driver in remove function.

Now ASoC has snd_soc_disconnect_sync() for this purpose.
Let's use it.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>