ALSA: hda - Fix misc workqueue issues

Some fixes regarding snd-hda-intel workqueue:
- Use create_singlethread_workqueue() instead of create_workqueue()
  as per-CPU work isn't required.
- Allocate workq name string properly
- Renamed the workq name to "hd-audio*" to be more obvious.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/pci/hda/hda_codec.h b/sound/pci/hda/hda_codec.h
index 5810ef5..09a332a 100644
--- a/sound/pci/hda/hda_codec.h
+++ b/sound/pci/hda/hda_codec.h
@@ -614,6 +614,7 @@
 
 	/* unsolicited event queue */
 	struct hda_bus_unsolicited *unsol;
+	char workq_name[16];
 	struct workqueue_struct *workq;	/* common workqueue for codecs */
 
 	/* assigned PCMs */