ALSA: usb-audio: Move rate validation quirk into quirk_flags

The rate validation at the device probe is applied only to the
specific devices (currently only for MOTU devices), and this check can
be moved to quirk_flags gracefully, too.

Link: https://lore.kernel.org/r/20210729074404.19728-1-tiwai@suse.de


Signed-off-by: Takashi Iwai <tiwai@suse.de>