docs: kernel_abi.py: make it compatible with Sphinx 1.7+

The same way kerneldoc.py needed changes to work with newer
Sphinx, this script needs the same changes.

While here, reorganize the include order to match kerneldoc.py.

Acked-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/f2b25caef5db7738629773a03463908d3b39b83a.1604042072.git.mchehab+huawei@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>