[util] Update `make_new_dif.py` to use `autogen_banner.py` module.

The autogen warning banner in the auto-generated DIF templates was not
populated by the `autogen_banner.py` module. This fixes that.

This is the final task that fixes #8142.

Signed-off-by: Timothy Trippel <ttrippel@google.com>
diff --git a/util/make_new_dif.py b/util/make_new_dif.py
index 7d06753..0a326fc 100755
--- a/util/make_new_dif.py
+++ b/util/make_new_dif.py
@@ -44,6 +44,7 @@
 
 from mako.template import Template
 
+from autogen_banner import get_autogen_banner
 from make_new_dif.ip import Ip
 
 # This file is $REPO_TOP/util/make_new_dif.py, so it takes two parent()
@@ -141,7 +142,12 @@
                                     strict_undefined=True)
 
                 # Generate output file.
-                out_file.write_text(template.render(ip=ip))
+                out_file.write_text(
+                    template.render(
+                        ip=ip,
+                        autogen_banner=get_autogen_banner(
+                            "util/make_new_dif.py --mode=regen --only=autogen",
+                            "//")))
 
                 # Format autogenerated file with clang-format.
                 assert (shutil.which("clang-format") and