Many PCI and other drivers performs snd_pcm_period_elapsed() simply in
its interrupt handler, so the sync_stop operation is just to call
synchronize_irq().  Instead of putting this call multiple times,
introduce the common card->sync_irq field.  When this field is set,
PCM core performs synchronize_irq() for sync-stop operation.  Each
driver just needs to copy its local IRQ number to card->sync_irq, and
that's all we need.

Link: https://lore.kernel.org/r/20191117085308.23915-8-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>