USB: Change the necessary defines to get debug output

While debugging some USB stuff, I've first missed that there are actually
two defines necessary to get usefull output. The one needed to get debug output
for the communication with HUBs was burried somewhere deep inside the code.

Change that so that a #define DEBUG is enough while still leaving the possibility
to reduce unwanted debug output.

Signed-off-by: Alexander Holler <holler@ahsoftware.de>

common/usb.c

@@ -55,7 +55,10 @@
 #include <asm/4xx_pci.h>
 #endif
 
-#undef USB_DEBUG
+#ifdef DEBUG
+#define USB_DEBUG
+#define USB_HUB_DEBUG
+#endif
 
 #ifdef	USB_DEBUG
 #define	USB_PRINTF(fmt, args...)	printf(fmt , ##args)
@@ -960,8 +963,6 @@ void usb_scan_devices(void)
  * Probes device for being a hub and configurate it
  */
 
-#undef	USB_HUB_DEBUG
-
 #ifdef	USB_HUB_DEBUG
 #define	USB_HUB_PRINTF(fmt, args...)	printf(fmt , ##args)
 #else