Fix more printf() format warnings

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
diff --git a/drivers/usb/usbdcore.c b/drivers/usb/usbdcore.c
index 808da9f..53ed669 100644
--- a/drivers/usb/usbdcore.c
+++ b/drivers/usb/usbdcore.c
@@ -552,7 +552,7 @@
 	struct urb *urb;
 
 	if (!(urb = (struct urb *) malloc (sizeof (struct urb)))) {
-		usberr (" F A T A L:  malloc(%u) FAILED!!!!",
+		usberr (" F A T A L:  malloc(%zu) FAILED!!!!",
 			sizeof (struct urb));
 		return NULL;
 	}