qconfig: Move arg checking a little higher

Check for scan_source as one of the possible operations for this tool,
moving the check above the scan_source implementation.

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

tools/qconfig.py

@@ -1534,14 +1534,15 @@ def main():
     col = terminal.Color(terminal.COLOR_NEVER if args.nocolour
                          else terminal.COLOR_IF_TERMINAL)
 
+    if not any((args.force_sync, args.build_db, args.imply, args.find,
+                args.scan_source)):
+        parser.print_usage()
+        sys.exit(1)
+
     if args.scan_source:
         do_scan_source(os.getcwd(), args.update)
         return 0
 
-    if not any((args.force_sync, args.build_db, args.imply, args.find)):
-        parser.print_usage()
-        sys.exit(1)
-
     # prefix the option name with CONFIG_ if missing
     configs = [prefix_config(cfg) for cfg in args.configs]