[ALSA] intel8x0 - Add spdif_aclink option

Added spdif_aclink module option to specify whether the board
has SPDIF over AC-link or a direct connection from the controller
chip.
NForce and ICH4 (or newer) boards may be equipped with SPDIF
through AC97 codec.  In such a case, SPDIF should be handled
as if the old ICH style (the same slot for analog and digital).
A quirk list is added to detect this automatically for known
hardwares.
Corresponds to ALSA bug#2637.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>