ALSA: usb-audio: Skip DSD quirk for Musical Fidelity M6s DAC

ALSA: usb-audio: Skip DSD quirk for Musical Fidelity M6s DAC

Salvador reported that the recent fix for applying the DSD quirk to
Musical Fidelity devices broke for his M6s DAC model (2772:0502).

Although this is basically a firmware bug, the model in question is
fairly old, and no further firmware update can be expected, so it'd be
better to address in the driver side.

As an ad hoc workaround, skip the DSD quirk for this device by adding
an empty quirk entry of 2772:0502; this essentially skips the later
DSD quirk entry by the match with the vendor 2772.

Fixes: da3a7efff64e ("ALSA: usb-audio: Update for native DSD support quirks")
Reported-by: Salvador Blaya <tiniebla6@gmail.com>
Closes: https://lore.kernel.org/CAOdyq+qFaqCh=tK_wNnA64hv5pQuA1Y09ANxQ=xK8yR-t4mf9Q@mail.gmail.com
Tested-by: Salvador Blaya <tiniebla6@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20260709095614.1418838-1-tiwai@suse.de