kernel: add missing symbol to usb-audio

Signed-off-by: John Crispin <[email protected]>

SVN-Revision: 48728

package/kernel/linux/modules/usb.mk

@@ -576,6 +576,7 @@ define KernelPackage/usb-audio
   TITLE:=Support for USB audio devices
   KCONFIG:= \
 	CONFIG_USB_AUDIO \
+	CONFIG_SND_USB=y \
 	CONFIG_SND_USB_AUDIO
   $(call AddDepends/usb)
   $(call AddDepends/sound)