CI: Install pylibfdt's requirements in the tool jobs

The GitLab and Azure tool-test and pylint jobs build the pylibfdt
bindings, which need setuptools. That currently comes only from patman's
requirements.txt, which a later patch drops. Install
scripts/dtc/pylibfdt/requirements.txt in those jobs, the proper source
for that dependency, so setuptools survives patman's removal.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>