ALSA: msnd: 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/20191210063454.31603-44-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/isa/msnd/msnd_pinnacle.c

@@ -538,6 +538,7 @@ static int snd_msnd_attach(struct snd_card *card)
 		printk(KERN_ERR LOGNAME ": Couldn't grab IRQ %d\n", chip->irq);
 		return err;
 	}
+	card->sync_irq = chip->irq;
 	if (request_region(chip->io, DSP_NUMIO, card->shortname) == NULL) {
 		free_irq(chip->irq, chip);
 		return -EBUSY;