ALSA: oxygen: add HiFier Serenade support

Add support for the TempoTec/MediaTek HiFier Serenade sound card.

The PCI ID was already there, but the driver handled it like the
Fantasia model, which resulted in a dummy recording device.  As
a stereo output-only card, this model is to be handled exactly
like the HG2PCI.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>