ALSA: docs: Update about the new PCM sync_stop ops

Add the documentation about the new PCM sync_stop ops and
card->sync_irq field.

Link: https://lore.kernel.org/r/20191117085308.23915-9-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
1 file changed