kmemleak: Do not warn if an unknown object is freed

vmap'ed memory blocks are not tracked by kmemleak (yet) but they may be
released with vfree() which is tracked. The corresponding kmemleak
warning is only enabled in debug mode. Future patch will add support for
ioremap and vmap.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

mm/kmemleak.c

@@ -531,8 +531,10 @@ static void delete_object(unsigned long ptr)
 	write_lock_irqsave(&kmemleak_lock, flags);
 	object = lookup_object(ptr, 0);
 	if (!object) {
+#ifdef DEBUG
 		kmemleak_warn("Freeing unknown object at 0x%08lx\n",
 			      ptr);
+#endif
 		write_unlock_irqrestore(&kmemleak_lock, flags);
 		return;
 	}