pylibfdt: Fix disable version normalization

On Arch Linux based systems python setuptools does not contain
"setuptools.extern" hence it is failing with the following
error-message:
"
ModuleNotFoundError: No module named 'setuptools.extern'
"

According to a eschwartz `setuptools.extern` is not a public API and
shall not be assumed to be present in the setuptools package. He
mentions that the setuptools project anyway wants to drop this. [1]

Use the correct solution introduced by python setuptools developers to
disable normalization. [2]

[1] https://bbs.archlinux.org/viewtopic.php?id=259608
[2] https://github.com/pypa/setuptools/pull/2026
Fixes: 440098c42e ("pylibfdt: Fix version normalization warning")
Signed-off-by: Philippe Schenker <philippe.schenker@toradex.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>

scripts/dtc/pylibfdt/setup.py

@@ -20,16 +20,12 @@ allows this script to be run stand-alone, e.g.:
     ./pylibfdt/setup.py install [--prefix=...]
 """
 
-from setuptools import setup, Extension
+from setuptools import setup, Extension, sic
 from setuptools.command.build_py import build_py as _build_py
-from setuptools.extern.packaging import version
 import os
 import re
 import sys
 
-# Disable version normalization
-version.Version = version.LegacyVersion
-
 srcdir = os.path.dirname(__file__)
 
 with open(os.path.join(srcdir, "../README"), "r") as fh:
@@ -141,7 +137,7 @@ class build_py(_build_py):
 
 setup(
     name='libfdt',
-    version=version,
+    version=sic(version),
     cmdclass = {'build_py' : build_py},
     author='Simon Glass',
     author_email='sjg@chromium.org',