[ALSA] usb-audio - enable high speed transfers with Audiy 2 NX

USB generic driver
This patch enables the boot commands to activate high speed mode (and
associated sample formats like 8 channels with 24 bits at 96 kHz) on the
SB Audigy 2 NX.

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