drivers/net/usb/Makefile - shrink logspam

When building with CONFIG_USB_DEBUG, don't create logspam from
the USB networking drivers.
Signed-off-by: NDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/usb/Makefile

@@ -20,6 +20,3 @@ obj-$(CONFIG_USB_NET_ZAURUS)	+= zaurus.o
 obj-$(CONFIG_USB_NET_MCS7830)	+= mcs7830.o
 obj-$(CONFIG_USB_USBNET)	+= usbnet.o
 
-ifeq ($(CONFIG_USB_DEBUG),y)
-EXTRA_CFLAGS += -DDEBUG
-endif