patman: fix installation of README.rst data file

This fixes a regression introduced in commit 74df491051 ("buildman:
Convert documentation to rST").

Signed-off-by: Maxim Cournoyer <maxim.cournoyer@savoirfairelinux.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

tools/patman/setup.py

@@ -7,6 +7,6 @@ setup(name='patman',
       scripts=['patman'],
       packages=['patman'],
       package_dir={'patman': ''},
-      package_data={'patman': ['README']},
+      package_data={'patman': ['README.rst']},
       classifiers=['Environment :: Console',
                    'Topic :: Software Development'])