binman: Move the main code into a function

Put this code into a function so it is easy for it be run when packaged.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/main.py b/tools/binman/main.py
index eef17b7..92d2431 100755
--- a/tools/binman/main.py
+++ b/tools/binman/main.py
@@ -85,7 +85,7 @@
 
     return (0 if result.wasSuccessful() else 1)
 
-def RunTestCoverage(toolpath):
+def RunTestCoverage(toolpath, build_dir):
     """Run the tests and check that we get 100% coverage"""
     glob_list = control.GetEntryModules(False)
     all_set = set([os.path.splitext(os.path.basename(item))[0]
@@ -97,7 +97,7 @@
     test_util.run_test_coverage('tools/binman/binman', None,
             ['*test*', '*main.py', 'tools/patman/*', 'tools/dtoc/*',
              'tools/u_boot_pylib/*'],
-            args.build_dir, all_set, extra_args or None)
+            build_dir, all_set, extra_args or None)
 
 def RunBinman(args):
     """Main entry point to binman once arguments are parsed
@@ -117,7 +117,7 @@
 
     if args.cmd == 'test':
         if args.test_coverage:
-            RunTestCoverage(args.toolpath)
+            RunTestCoverage(args.toolpath, args.build_dir)
         else:
             ret_code = RunTests(args.debug, args.verbosity, args.processes,
                                 args.test_preserve_dirs, args.tests,
@@ -141,8 +141,12 @@
     return ret_code
 
 
-if __name__ == "__main__":
+def start_binman():
     args = cmdline.ParseArgs(sys.argv[1:])
 
     ret_code = RunBinman(args)
     sys.exit(ret_code)
+
+
+if __name__ == "__main__":
+    start_binman()