ALSA: hda - Use ALC_INIT_DEFAULT for really default initialization

When SKU assid gives no valid bits for 0x38, the driver didn't take
any action, so far.  This resulted in the missing initialization for
external amps, etc, thus the silent output in the end.

Especially users hit this problem on ALC888 newly since 2.6.35,
where the driver doesn't force to use ALC_INIT_DEFAULT any more.

This patch sets the default initialization scheme to use
ALC_INIT_DEFAULT when no valid bits are set for SKU assid.

Reference:
	https://bugzilla.redhat.com/show_bug.cgi?id=657388



Reported-and-tested-by: Kyle McMartin <kyle@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>