ALSA: hda - Fix missing fixup for Mac Mini with STAC9221

A fixup for Apple Mac Mini was lost during the adaption to the generic
parser because the fallback for the generic ID 8384:7680 was dropped,
and it resulted in the silence output (and maybe other problems).

Unfortunately, just adding the missing subsystem ID wasn't enough, in
this case.  The subsystem ID of this machine is 0000:0100 (what Apple
thought...?), and since snd_hda_pick_fixup() doesn't take the vendor
id zero into account, the driver ignored this entry.  Now it's fixed
to regard the vendor id zero as a valid value.

Reported-and-tested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: <stable@vger.kernel.org> [v3.9+]
Signed-off-by: Takashi Iwai <tiwai@suse.de>