ALSA: usb-audio: Add quirks for Audio Kontrol 6

This new device by Native Instruments is also compliant to the USB
standard v2.0, but hides this detail at when connected.

It needs the same boot quirks than other models, and also has two
non-class-compliant mixer controls.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>