ALSA: usb-audio: RME Babyface Pro mixer patch

Added mixer quirks to allow controlling the internal DSP of the
RME Babyface Pro and its successor Babyface Pro FS.
Signed-off-by: Thomas Ebeling <penguins@bollie.de>
Link: https://lore.kernel.org/r/20200414211019.qprg7whepg2y7nei@bollie.ca9.euSigned-off-by: Takashi Iwai <tiwai@suse.de>