buildman: Drop some unnecessary variables

Drop some variables at the end of the do_bulidman() function.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/buildman/control.py b/tools/buildman/control.py
index 9f775cb..f30b8be 100644
--- a/tools/buildman/control.py
+++ b/tools/buildman/control.py
@@ -616,9 +616,5 @@
 
     TEST_BUILDER = builder
 
-    # Work out which boards to build
-    board_selected = brds.get_selected_dict()
-
-    commits = series.commits if series else None
-    retval = run_builder(builder, commits, board_selected, options)
-    return retval
+    return run_builder(builder, series.commits if series else None,
+                       brds.get_selected_dict(), options)