ALSA: usb-audio: Add support for Zoom R16/24 capture and midi interfaces

This makes the midi interface and capture work out of the box with
R16 (and presumably R24 too but untested). Playback stream would also
seem to function fine except for one caveat: no sound is produced,
so it is disabled for now. Mixer descriptors are garbage and will
require further quirks to enable functionality, also disabled here.

Signed-off-by: Panu Matilainen <pmatilai@laiskiainen.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>