ALSA: usb-audio: Generic DSD detection for XMOS-based implementations

Use more generic method to detect DSD capability of XMOS-based UAC2
implementations in order to support future devices without having to
explicitly list every device separately.

Signed-off-by: Jussi Laako <jussi@sonarnerd.net>
Signed-off-by: Takashi Iwai <tiwai@suse.de>