Introduce a table containing the pins and their jack-detection states
for avoiding the unnecessary verbs to check the pin status at each time.

When the unsol event is enabled via snd_hda_jack_detect_enable(), it
automatically adds the given NID to the table.  Then the driver supposes
that the codec driver will set the dirty flag appropariately when an
unsolicited event is invoked for that pin.

The behavior for reading other pins that aren't registered in the table
doesn't change.  Only the pins assigned to the table are cached, so far.

In near futre, this table can be extended to use the central place for
the unsolicited events of all pins, etc, and eventually include the
jack-detect kcontrols that replace the current input-jack stuff.

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