ALSA: usb-audio: add native DSD support for Matrix Audio DACs

This patch adds native DSD support for two XMOS based DACs from Matrix Audio:
- X-Sabre
- Mini-i Pro

Signed-off-by: Jurgen Kramer <gtmkramer@xs4all.nl>
Signed-off-by: Takashi Iwai <tiwai@suse.de>