ALSA: hda - Implement unbind more safely

Now we have all pieces ready, and put them into places:
- add the hda_pcm refcount to azx_pcm_open() and azx_pcm_close(),
- call the most of cleanup code in hda_codec_reset() from the codec
  driver remove,
- call the same code also from the hda_codec object free.

Then the codec driver can be unbound more safely now.

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