ALSA: oxygen - Add a SSID for CMI8787-HG2PCI

This board has a strange PCI SSID 13f6:ffff.  Works as compabile as
MODEL_CMEDIA_REF.

Reported-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>