ALSA: fm801: 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/20191210063454.31603-21-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/fm801.c

@@ -1223,6 +1223,7 @@ static int snd_fm801_create(struct snd_card *card,
 			return -EBUSY;
 		}
 		chip->irq = pci->irq;
+		card->sync_irq = chip->irq;
 		pci_set_master(pci);
 	}