[ALSA] usb-audio - enable high speed (not) on Audigy 2 NX

USB generic driver
The SB Audigy 2 NX needs a special boot-up command before it works in
high speed mode.

However, we don't actually enable it yet because high speed
synchronization doesn't seem to work with this device.

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