ALSA: hda - Fix Oops at codec reset/reconfig

ALSA: hda - Fix Oops at codec reset/reconfig

commit 07dc59f0988cb54fd87bd373b3b27eb2401dd811 upstream.

snd_hda_codec_reset() calls restore_pincfgs() where the codec is
powered up again, which eventually tries to resume and initialize via
the callbacks of the codec.  However, it's the place just after codec
free callback, thus no codec callbacks should be called after that.
On a codec like CS4206, it results in Oops due to the access in init
callback.

This patch fixes the issue by clearing the codec callbacks properly
after freeing codec.

Reported-by: Daniel J Blueman <daniel@quora.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>