Now we create the standard HD-audio bus (/sys/bus/hdaudio), and bind
the codec driver with the codec device over there.  This is the first
step of the whole transition so that the changes to each codec driver
are kept as minimal as possible.

Each codec driver needs to register hda_codec_driver struct containing
the currently existing preset via the new helper macro
module_hda_codec_driver().  The old hda_codec_preset_list is replaced
with this infrastructure.  The generic parsers (for HDMI and other)
are also included in the preset with the special IDs to bind
uniquely.

In HD-audio core side, the device binding code is split to
hda_bind.c.  It provides the snd_hda_bus_type implementation to match
the codec driver with the given codec vendor ID.  It also manages the
module auto-loading by itself like before: when the matching isn't
found, it tries to probe the corresponding codec modules, and finally
falls back to the generic drivers.  (The special ID mentioned above is
set at this stage.)

The only visible change to outside is that the hdaudio sysfs entry now
appears in /sys/bus/devices, not as a sound class device.

More works to move the suspend/resume and remove ops will be
(hopefully) done in later patches.
Signed-off-by: Takashi Iwai <tiwai@suse.de>