ASoC: component: Add sync_stop PCM ops

Add the support of the new PCM sync_stop ops in ASoC component.
It's optional and can be NULL unless you need the sync operation.

Acked-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20191121190709.29121-3-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>