ALSA: usb-audio: Add Pioneer DJ DJM-900NXS2 support

Pioneer DJ DJM-900NXS2 is a widely used DJ mixer with 2 audio USB
interfaces. Both have a MIDI controller, 10 playback and 12 capture
channels. Audio endpoints are vendor-specific and 3 files need to be
patched. All playback and capture channels work fine with all supported
sample rates (44.1k, 48k, 96k). Patches are attached.

Signed-off-by: Dmitry Panchenko <dmitry@d-systems.ee>
Link: https://lore.kernel.org/r/48ab19ff-3303-9bf8-ed0e-bcb31d8537eb@d-systems.ee
Signed-off-by: Takashi Iwai <tiwai@suse.de>