ALSA: usb-audio: add support for E-Mu Tracker Pre

Add support for the E-Mu "Tracker Pre" USB sound card, following
the example of the (very similar) E-Mu 0202 and E-Mu 0404 USB.

As with the 0202 and 0404 USB, functionality is very limited:
just a couple of sample rates, no volume/mute control, etc.

Signed-off-by: Eran Tromer <eran@tromer.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>