ALSA: pdaudiocf: Support PCM sync_stop

The driver invokes snd_pcm_period_elapsed() simply from the threaded
interrupt handler.  Set card->sync_irq for enabling the missing
sync_stop PCM operation.

Link: https://lore.kernel.org/r/20191210063454.31603-54-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/pcmcia/pdaudiocf/pdaudiocf.c

@@ -224,6 +224,7 @@ static int pdacf_config(struct pcmcia_device *link)
 					link->irq) < 0)
 		goto failed;
 
+	pdacf->card->sync_irq = link->irq;
 	return 0;
 
  failed: