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

Added snd_ctl_add_slave_uncached() function to add a slave element
with volatile controls.  The values of normal slave elements are
supposed to be cachable, i.e. they are changed only via the put
callbacks.  OTOH, when a slave element is volatile and its values may
be changed by other reason (e.g. hardware status change), the values
will get inconsistent.

The new function allows the slave elements with volatile changes.
When the slave is tied with this call, the native get callback is
issued at each time so that the values are always updated.
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

Use a private array for TLV entries of virtual master controls instead
of (supposed) static array.  This cleans up the existing codes.

Also, now vmaster assumes the simple dB-range TLV that is the only type
it can handle.
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

Move the codes for virtual master controls to sound core part so that
not only hda-intel drivers can use it.
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

Added helper functions to implement virtual master volume controls.
The virtual master control is a control element that has multiple
slave controls.  The value of master element is equally added to
slave elements.
The functions are written for general purpose, but it's put in the
HD-audio directory as now, since HD-audio driver is the only user.
It should be moved to the common place once after other drivers use
vmaster.
Signed-off-by: NTakashi Iwai <tiwai@suse.de>
Signed-off-by: NJaroslav Kysela <perex@perex.cz>