ALSA: usb-audio: add Starr Labs USB MIDI support

Add support for Starr Labs USB MIDI devices such as the Z7S, which are
based on an FTDI serial UART chip.

Based on a patch by Daniel Mack.

Signed-off-by: Kristian Amlie <kristian@amlie.name>
Acked-by: Daniel Mack <zonque@gmail.com>
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/usb/usbaudio.h b/sound/usb/usbaudio.h
index 1e79986..3e2b035 100644
--- a/sound/usb/usbaudio.h
+++ b/sound/usb/usbaudio.h
@@ -80,6 +80,7 @@
 	QUIRK_MIDI_CME,
 	QUIRK_MIDI_AKAI,
 	QUIRK_MIDI_US122L,
+	QUIRK_MIDI_FTDI,
 	QUIRK_AUDIO_STANDARD_INTERFACE,
 	QUIRK_AUDIO_FIXED_ENDPOINT,
 	QUIRK_AUDIO_EDIROL_UAXX,