usb: change to new flag variable

Replace EXTRA_CFLAGS with ccflags-y.

Signed-off-by: matt mooney <mfm@muteddisk.com>
Acked-by: WANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/core/Makefile b/drivers/usb/core/Makefile
index ec16e602..17c8e2d 100644
--- a/drivers/usb/core/Makefile
+++ b/drivers/usb/core/Makefile
@@ -16,6 +16,4 @@
 
 obj-$(CONFIG_USB)	+= usbcore.o
 
-ifeq ($(CONFIG_USB_DEBUG),y)
-EXTRA_CFLAGS += -DDEBUG
-endif
+ccflags-$(CONFIG_USB_DEBUG) := -DDEBUG