ALSA: ad1816a: 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/20191210063454.31603-40-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/isa/ad1816a/ad1816a_lib.c

@@ -597,6 +597,7 @@ int snd_ad1816a_create(struct snd_card *card,
 		return -EBUSY;
 	}
 	chip->irq = irq;
+	card->sync_irq = chip->irq;
 	if (request_dma(dma1, "AD1816A - 1")) {
 		snd_printk(KERN_ERR "ad1816a: can't grab DMA1 %d\n", dma1);
 		snd_ad1816a_free(chip);