docs-rst: add dev-tools book to pdf output

The dev-tools API book was added without the bits required to
generate PDF output at the main conf.py. Add them.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Documentation/conf.py

@@ -353,6 +353,8 @@ latex_documents = [
      'The kernel development community', 'manual'),
     ('crypto/index', 'crypto-api.tex', 'Linux Kernel Crypto API manual',
      'The kernel development community', 'manual'),
+    ('dev-tools/index', 'dev-tools.tex', 'Development tools for the Kernel',
+     'The kernel development community', 'manual'),
     ('doc-guide/index', 'kernel-doc-guide.tex', 'Linux Kernel Documentation Guide',
      'The kernel development community', 'manual'),
     ('driver-api/index', 'driver-api.tex', 'The kernel driver API manual',