dtoc: Fix fdt test coverage

Fix a bug that the --processes option was ignored, thus resulting in no
test coverage information being generated.

Signed-off-by: Simon Glass <sjg@chromium.org>
Fixes: 42ae363ddd9 ("dtoc: Update fdt tests to use test_util")
diff --git a/tools/dtoc/test_fdt.py b/tools/dtoc/test_fdt.py
index b488198..afa0bb5 100755
--- a/tools/dtoc/test_fdt.py
+++ b/tools/dtoc/test_fdt.py
@@ -793,7 +793,7 @@
     """
     test_name = args[0] if args else None
     result = test_util.run_test_suites(
-        'test_fdt', False, False, False, None, test_name, None,
+        'test_fdt', False, False, False, processes, test_name, None,
         [TestFdt, TestNode, TestProp, TestFdtUtil])
 
     return (0 if result.wasSuccessful() else 1)