[ALSA] USB midi: Remove duplicate CS_AUDIO_* #defines

Removed the CS_AUDIO_* #defines, which were duplicates of the
class-specific USB_DT_CS_* #defines in <linux/usb_ch9.h>.

Signed-off-by: Ben Williamson <ben.williamson@greyinnovation.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/usb/usbmidi.c b/sound/usb/usbmidi.c
index 5c53ec8..5105b6b 100644
--- a/sound/usb/usbmidi.c
+++ b/sound/usb/usbmidi.c
@@ -1413,7 +1413,7 @@
 	for (cs_desc = hostif->extra;
 	     cs_desc < hostif->extra + hostif->extralen && cs_desc[0] >= 2;
 	     cs_desc += cs_desc[0]) {
-		if (cs_desc[1] == CS_AUDIO_INTERFACE) {
+		if (cs_desc[1] == USB_DT_CS_INTERFACE) {
 			if (cs_desc[2] == MIDI_IN_JACK)
 				endpoint->in_cables = (endpoint->in_cables << 1) | 1;
 			else if (cs_desc[2] == MIDI_OUT_JACK)