of: Use NULL for pointers

Commit 4485681939b9 (of/fdt: Clean up casting in unflattening path)
modified unflatten_dt_node() to take a void * for the mem parameter
instead of an unsigned long. One of the call sites wasn't updated.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Grant Likely <grant.likely@linaro.org>

Conflicts:
	drivers/of/fdt.c

drivers/of/fdt.c

@@ -324,7 +324,7 @@ static void __unflatten_device_tree(void *blob,
 
 	/* First pass, scan for size */
 	start = 0;
-	size = (unsigned long)unflatten_dt_node(blob, 0, &start, NULL, NULL, 0);
+	size = (unsigned long)unflatten_dt_node(blob, NULL, &start, NULL, NULL, 0);
 	size = ALIGN(size, 4);
 
 	pr_debug("  size is %lx, allocating...\n", size);