ALSA: trident: 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/20191210063454.31603-37-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/trident/trident_main.c

@@ -3543,6 +3543,7 @@ int snd_trident_create(struct snd_card *card,
 		return -EBUSY;
 	}
 	trident->irq = pci->irq;
+	card->sync_irq = trident->irq;
 
 	/* allocate 16k-aligned TLB for NX cards */
 	trident->tlb.entries = NULL;