ALSA: usb-audio: Add support for Akai MPC Element USB MIDI controller

The Akai MPC Element incorrectly reports its bInterfaceClass as 255, but
otherwise implements the USB MIDI spec correctly.

This adds a quirks-table.h entry which allows the device to be
recognized as a standard USB MIDI device.

Signed-off-by: Paul Bonser <misterpib@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/quirks-table.h

@@ -2486,6 +2486,28 @@ YAMAHA_DEVICE(0x7010, "UB99"),
 	}
 },
 
+{
+	/* Akai MPC Element */
+	USB_DEVICE(0x09e8, 0x0021),
+	.driver_info = (unsigned long) & (const struct snd_usb_audio_quirk) {
+		.ifnum = QUIRK_ANY_INTERFACE,
+		.type = QUIRK_COMPOSITE,
+		.data = & (const struct snd_usb_audio_quirk[]) {
+			{
+				.ifnum = 0,
+				.type = QUIRK_IGNORE_INTERFACE
+			},
+			{
+				.ifnum = 1,
+				.type = QUIRK_MIDI_STANDARD_INTERFACE
+			},
+			{
+				.ifnum = -1
+			}
+		}
+	}
+},
+
 /* TerraTec devices */
 {
 	USB_DEVICE_VENDOR_SPEC(0x0ccd, 0x0012),