of: unittest: fix an error test in of_unittest_overlay_8()

We changed this from of_overlay_apply() to overlay_data_apply().  The
overlay_data_apply() function returns 1 on success and 0 on error so
the check for less than zero needs to be updated.

Fixes: 39a751a4 ("of: change overlay apply input data from unflattened to FDT")
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: NFrank Rowand <frowand.list@gmail.com>
Signed-off-by: NRob Herring <robh@kernel.org>

drivers/of/unittest.c

@@ -1696,8 +1696,7 @@ static void __init of_unittest_overlay_8(void)
 
 		overlay_name = overlay_name_from_nr(overlay_nr + i);
 
-		ret = overlay_data_apply(overlay_name, &ovcs_id);
-		if (ret < 0)  {
+		if (!overlay_data_apply(overlay_name, &ovcs_id)) {
 			unittest(0, "could not apply overlay \"%s\"\n",
 					overlay_name);
 			return;