Update find_patches to python3

The `find_patches.py` utility was python2. Update it to python3.
In addition:

- Re-run it to get the latest version of `README.patches`
- Update the copyright headers to the new style

Bug: chromium:1409095
Change-Id: I4181e6abd9242cf9da86b1da3f3920bcee4ad819
diff --git a/generate_nasm_sources.py b/generate_nasm_sources.py
index 356cb47..4621c7e 100755
--- a/generate_nasm_sources.py
+++ b/generate_nasm_sources.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 #
-# Copyright 2018 The Chromium Authors. All rights reserved.
+# Copyright 2018 The Chromium Authors
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.