ALSA: usb-audio: Add support for Pioneer DJ DDJ-RR controller

This patch allows the Pioneer DJ DDJ-RR to be seen as a USB audio
device under Linux and therefore usable in such applications as
Mixxx.

Tested Master Audio out, headphones (both output jacks) and microphone
input. All work perfectly.

Signed-off-by: Daniel Martin <dmanlfc@gmail.com>
Link: https://lore.kernel.org/r/20201128084035.2958-1-tiwai@suse.de


Signed-off-by: Takashi Iwai <tiwai@suse.de>