Gateway notebooks have their ID inside codec vendor ID, not at PCI ID. Due to
that, model auto-detection were not possible with the standard seek method.

This is what is found at lspci -vnn:

00:14.2 Audio device [0403]: ATI Technologies Inc SB450 HDA Audio [1002:437b] (rev 01)
        Subsystem: ATI Technologies Inc SB450 HDA Audio [1002:437b]

Yet, autodetection is possible, since the codec properly reflects the vendor at
the Subsystem ID:

$ cat /proc/asound/card0/codec#0 |head -4

Codec: SigmaTel STAC9250
Address: 0
Vendor Id: 0x83847634
Subsystem Id: 0x107b0367

This patch adds a new autodetection function that seeks for codec subsystem ID.
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>