Create kcontrols for pin jack-detections, which work similarly like
jack-input layer.  Each control will notify when the jack is plugged or
unplugged, and also user can read the value at any time via the normal
control API.

The control elements are created with iface=CARD, so that they won't
appear in the mixer apps.

So far, only the pins that enabled the jack-detection are registered.
For covering all pins, the transition of the common unsol-tag handling
would be needed.  Stay tuned.
Signed-off-by: Takashi Iwai <tiwai@suse.de>