ALSA: hda - introduce HDA_SUBDEV_AMP_FLAG (ControlAmp in proc)

The purpose of this changeset is to show information about amplifier
setting in the codec proc file. Something like:

  Control: name="Front Playback Volume", index=0, device=0
    ControlAmp: chs=3, dir=Out, idx=0, ofs=0
  Control: name="Front Playback Switch", index=0, device=0
    ControlAmp: chs=3, dir=In, idx=2, ofs=0

Signed-off-by: Jaroslav Kysela <perex@perex.cz>
diff --git a/sound/pci/hda/patch_via.c b/sound/pci/hda/patch_via.c
index 64995e8..b94cdee 100644
--- a/sound/pci/hda/patch_via.c
+++ b/sound/pci/hda/patch_via.c
@@ -458,7 +458,9 @@
 	if (!knew->name)
 		return -ENOMEM;
 	if (get_amp_nid_(val))
-		knew->subdevice = HDA_SUBDEV_NID_FLAG | get_amp_nid_(val);
+		knew->subdevice = HDA_SUBDEV_NID_FLAG |
+				  HDA_SUBDEV_AMP_FLAG |
+				  get_amp_nid_(val);
 	knew->private_value = val;
 	return 0;
 }