Afer commit aa202455 , none of realtek
codec has hardware volume control "PCM Playback Volume" and
"PCM Playback Switch".

As Virtual Master require all slave controls must have same number of step
and dB range.
Signed-off-by: NRaymond Yau <superquad.vortex2@gmail.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>