[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/usbaudio.c b/sound/usb/usbaudio.c
index 30cadec..627de95 100644
--- a/sound/usb/usbaudio.c
+++ b/sound/usb/usbaudio.c
@@ -2981,7 +2981,7 @@
 		return -ENXIO;
 	alts = &iface->altsetting[1];
 	altsd = get_iface_desc(alts);
-	if (alts->extralen != 11 || alts->extra[1] != CS_AUDIO_INTERFACE ||
+	if (alts->extralen != 11 || alts->extra[1] != USB_DT_CS_INTERFACE ||
 	    altsd->bNumEndpoints != 1)
 		return -ENXIO;