ALSA: Document tyan model for Realtek ALC262

As just pointed out to me, the new tyan model for ALC262 was
implemented but not documented. This adds the board to the
list, using both its marketing name (Thunder n6650W) and its
model number (S2915-E).

Signed-off-by: Tony Vroon <tony@linx.net>
Signed-off-by: Takashi Iwai <tiwai@suse.de>