[ALSA] sound/pci/hda: use create_singlethread_workqueue()

process_unsol_events() seems to assume a singlethread one (IOW, racey).
So, this patch uses create_singlethread_workqueue() instead of
create_workqueue().
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/hda/hda_codec.c

@@ -295,7 +295,7 @@ static int init_unsol_queue(struct hda_bus *bus)
 		snd_printk(KERN_ERR "hda_codec: can't allocate unsolicited queue\n");
 		return -ENOMEM;
 	}
-	unsol->workq = create_workqueue("hda_codec");
+	unsol->workq = create_singlethread_workqueue("hda_codec");
 	if (! unsol->workq) {
 		snd_printk(KERN_ERR "hda_codec: can't create workqueue\n");
 		kfree(unsol);