ALSA: hda - Add widget sysfs tree

ALSA: hda - Add widget sysfs tree

This patch changes the sysfs files assigned to the codec device on the
bus which were formerly identical with hwdep sysfs files.  Now it
shows only a few core parameter, vendor_id, subsystem_id, revision_id,
afg, mfg, vendor_name and chip_name.

In addition, now a widget tree is added to the bus device sysfs
directory for showing the widget topology and attributes.  It's just a
flat tree consisting of subdirectories named as the widget NID
including various attributes like widget capability bits.  The AFG
(usually NID 0x01) is always found there, and it contains always
amp_in_caps, amp_out_caps and power_caps files.  Each of these
attributes show a single value.  The rest are the widget nodes
belonging to that AFG.  Note that the child node might not start from
0x02 but from another value like 0x0a.

Each child node may contain caps, pin_caps, amp_in_caps, amp_out_caps,
power_caps and connections files.  The caps (representing the widget
capability bits) always contain a value.  The rest may contain
value(s) if the attribute exists on the node.  Only connections file
show multiple values while other attributes have zero or one single
value.

An example of ls -R output is like below:
% ls -R /sys/bus/hdaudio/devices/hdaudioC0D0/
/sys/bus/hdaudio/devices/hdaudioC0D0/widgets/:
01/  04/  07/  0a/  0d/  10/  13/  16/  19/  1c/  1f/  22/
02/  05/  08/  0b/  0e/  11/  14/  17/  1a/  1d/  20/  23/
03/  06/  09/  0c/  0f/  12/  15/  18/  1b/  1e/  21/

/sys/bus/hdaudio/devices/hdaudioC0D0/widgets/01:
amp_in_caps  amp_out_caps  power_caps

/sys/bus/hdaudio/devices/hdaudioC0D0/widgets/02:
amp_in_caps  amp_out_caps  caps  connections  pin_caps  pin_cfg
power_caps

/sys/bus/hdaudio/devices/hdaudioC0D0/widgets/03:
.....

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