[ALSA] ice1724 - Add support for Prodigy 7.1 XT

This patch supports Audiotrack 7.1 XT.
7.1XT is almost same hardware as 7.1LT. so using 7.1 LT's code.

Signed-off-by: Toshimune Konno <heitouk@nifty.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>