ALSA: emu10k1: 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/20191210063454.31603-17-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/emu10k1/emu10k1_main.c

@@ -1984,6 +1984,7 @@ int snd_emu10k1_create(struct snd_card *card,
 		goto error;
 	}
 	emu->irq = pci->irq;
+	card->sync_irq = emu->irq;
 
 	/*
 	 *  Init to 0x02109204 :

sound/pci/emu10k1/emu10k1x.c

@@ -930,6 +930,7 @@ static int snd_emu10k1x_create(struct snd_card *card,
 		return -EBUSY;
 	}
 	chip->irq = pci->irq;
+	card->sync_irq = chip->irq;
   
 	if (snd_dma_alloc_pages(SNDRV_DMA_TYPE_DEV, &pci->dev,
 				4 * 1024, &chip->dma_buffer) < 0) {