ALSA: als300: 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/20191210063454.31603-4-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/als300.c

@@ -664,7 +664,7 @@ static int snd_als300_create(struct snd_card *card,
 		return -EBUSY;
 	}
 	chip->irq = pci->irq;
-
+	card->sync_irq = chip->irq;
 
 	snd_als300_init(chip);