[ALSA] usb-audio: fix non-48k sample rates with SB Audigy 2 ZS

Modules: USB generic driver

On the Audigy 2 ZS, disable all sample rate that are not a multiple of
48 kHz because the others work only with the digital output which is
not yet supported.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>