ALSA: bt87x: 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, as well as removing the superfluous synchronize_irq()
call.

Link: https://lore.kernel.org/r/20191210063454.31603-9-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/bt87x.c

@@ -751,8 +751,8 @@ static int snd_bt87x_create(struct snd_card *card,
 		goto fail;
 	}
 	chip->irq = pci->irq;
+	card->sync_irq = chip->irq;
 	pci_set_master(pci);
-	synchronize_irq(chip->irq);
 
 	err = snd_device_new(card, SNDRV_DEV_LOWLEVEL, chip, &ops);
 	if (err < 0)