Fix USB gadget net2280.c compile

It would fail the compile due to the newly added error checking testing
a bad macro for a "return value" unless USB_GADGET_DEBUG_FILES was
enabled.

Pointed out by Stephen Hemminger.
Acked-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/usb/gadget/net2280.c

@@ -1774,8 +1774,8 @@ static DEVICE_ATTR (queues, S_IRUGO, show_queues, NULL);
 
 #else
 
-#define device_create_file(a,b)	do {} while (0)
-#define device_remove_file	device_create_file
+#define device_create_file(a,b)	(0)
+#define device_remove_file(a,b)	do { } while (0)
 
 #endif