ALSA: riptide: Support PCM sync_stop

The driver invokes snd_pcm_period_elapsed() simply from the interrupt
handler.  Set card->sync_irq for enabling the missing sync_stop PCM
operation.

Link: https://lore.kernel.org/r/20191210063454.31603-31-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/riptide/riptide.c

@@ -1864,6 +1864,7 @@ snd_riptide_create(struct snd_card *card, struct pci_dev *pci,
 		return -EBUSY;
 	}
 	chip->irq = pci->irq;
+	card->sync_irq = chip->irq;
 	chip->device_id = pci->device;
 	pci_set_master(pci);
 	if ((err = snd_riptide_initialize(chip)) < 0) {