contrib/struct_endianness.py: simplify file extension check

Change-Id: Iaf7194fdfc3772973f9a9c806d375a9a56ff57c8
diff --git a/contrib/struct_endianness.py b/contrib/struct_endianness.py
index 2601869..e6cbe00 100755
--- a/contrib/struct_endianness.py
+++ b/contrib/struct_endianness.py
@@ -261,7 +261,7 @@
         return body_str
 
 def _check_file(f):
-    if not (f.endswith('.h') or f.endswith('.c') or f.endswith('.cpp')):
+    if not f.endswith(('.h', '.c', '.cpp')):
         return
 
     # section the file into