Added callbacks for a generic bind-control of mixer elements.
This can be used for creating a mixer element controlling multiple
widgets at the same time.  Two macros, HDA_BIND_VOL() and HDA_BIND_SW(),
are introduced for creating bind-volume and bind-switch, respectively.
It taks the mixer element name and struct hda_bind_ctls pointer, which
contains the real control callbacks in ops field and long array for
private_value of each bound widget.
All widgets have to be the same type (i.e. the same amp capability).
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>