If the cb function is already registered, should return the pointer
of the structure hda_jack_callback which contains this cb func, but
instead it returns the NULL.

Now fix it by replacing func_is_already_in_callback_list() with
find_callback_from_list().

Fixes: f4794c60 ("ALSA: hda - Don't register a cb func if it is registered already")
Reported-and-suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Hui Wang <hui.wang@canonical.com>
Link: https://lore.kernel.org/r/20201022030221.22393-1-hui.wang@canonical.comSigned-off-by: Takashi Iwai <tiwai@suse.de>