ALSA: usb-audio: Disable sample read check if firmware doesn't give back

Some buggy firmware don't give the current sample rate but leaves
zero.  Handle this case more gracefully without warning but just skip
the current rate verification from the next time.

Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20201218145858.2357-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>