[ALSA] Move vmaster code to sound core

Move the codes for virtual master controls to sound core part so that
not only hda-intel drivers can use it.

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

include/sound/control.h

@@ -169,4 +169,11 @@ int snd_ctl_boolean_mono_info(struct snd_kcontrol *kcontrol,
 int snd_ctl_boolean_stereo_info(struct snd_kcontrol *kcontrol,
 				struct snd_ctl_elem_info *uinfo);
 
+/*
+ * virtual master control
+ */
+struct snd_kcontrol *snd_ctl_make_virtual_master(char *name,
+						 const unsigned int *tlv);
+int snd_ctl_add_slave(struct snd_kcontrol *master, struct snd_kcontrol *slave);
+		      
 #endif	/* __SOUND_CONTROL_H */