ALSA: pcxhr: 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/20191210063454.31603-52-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/pcxhr/pcxhr.c

@@ -1190,6 +1190,7 @@ static int pcxhr_create(struct pcxhr_mgr *mgr,
 	chip->card = card;
 	chip->chip_idx = idx;
 	chip->mgr = mgr;
+	card->sync_irq = mgr->irq;
 
 	if (idx < mgr->playback_chips)
 		/* stereo or mono streams */