of: unittest: fix memory leak in unittest_data_add

In unittest_data_add, a copy buffer is created via kmemdup. This buffer
is leaked if of_fdt_unflatten_tree fails. The release for the
unittest_data buffer is added.

Fixes: b951f9dc ("Enabling OF selftest to run without machine's devicetree")
Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
Reviewed-by: Frank Rowand <frowand.list@gmail.com>
Signed-off-by: Rob Herring <robh@kernel.org>

drivers/of/unittest.c

@@ -1207,6 +1207,7 @@ static int __init unittest_data_add(void)
 	of_fdt_unflatten_tree(unittest_data, NULL, &unittest_data_node);
 	if (!unittest_data_node) {
 		pr_warn("%s: No tree to attach; not running tests\n", __func__);
+		kfree(unittest_data);
 		return -ENODATA;
 	}