ALSA: hda - Add "PCM" volume to vmaster slave list

The new parser may use "PCM" volume, but it was missing the vmaster
slave list, thus "Master" volume didn't control it.

Reference: https://bugzilla.kernel.org/show_bug.cgi?id=41342

Signed-off-by: Takashi Iwai <tiwai@suse.de>