ALSA: usb-audio: FIX native DSD support for TEAC UD-501 DAC

There are two versions of TEAC UD-501, the normal version and
the vendor updated version(UD-501V2).

They have the same VID/PID, but the num of the altsetting is different,
UD-501 has 2 altsets for stream, and UD-501V2 has 3.

So, add the logic to distinguish them by the Product Name, not by the PID.

Signed-off-by: Nobutaka Okabe <nob77413@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>