dtoc: Rename the main module

Python does not like the module name being the same as the module
directory. To allow dtoc modules to be used from other tools, rename
it.

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

tools/dtoc/dtoc

@@ -1 +1 @@
-dtoc.py
+main.py

tools/dtoc/main.py

@@ -77,7 +77,7 @@ def run_tests(args):
 def RunTestCoverage():
     """Run the tests and check that we get 100% coverage"""
     sys.argv = [sys.argv[0]]
-    test_util.RunTestCoverage('tools/dtoc/dtoc.py', '/dtoc.py',
+    test_util.RunTestCoverage('tools/dtoc/dtoc', '/main.py',
             ['tools/patman/*.py', '*/fdt*', '*test*'], options.build_dir)