dtoc: Use None to mean stdout

At present dtoc uses '-' internally to mean that output should go to
stdout. This is not necessary and None is more convenient. Update it.

Signed-off-by: Simon Glass <sjg@chromium.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/tools/dtoc/test_dtoc.py b/tools/dtoc/test_dtoc.py
index 4bf90444e1..41a10eb400 100755
--- a/tools/dtoc/test_dtoc.py
+++ b/tools/dtoc/test_dtoc.py
@@ -875,7 +875,7 @@ U_BOOT_DEVICE(spl_test2) = {
         """Test output to stdout"""
         dtb_file = get_dtb_file('dtoc_test_simple.dts')
         with test_util.capture_sys_output() as _:
-            self.run_test(['struct'], dtb_file, '-')
+            self.run_test(['struct'], dtb_file, None)
 
     def test_no_command(self):
         """Test running dtoc without a command"""