docs: Fix conf.py for Sphinx 2.0

commit 3bc8088464712fdcb078eefb68837ccfcc413c88 upstream.

Our version check in Documentation/conf.py never envisioned a world where
Sphinx moved beyond 1.x.  Now that the unthinkable has happened, fix our
version check to handle higher version numbers correctly.

Signed-off-by: Jonathan Corbet <corbet@lwn.net>
[rebase for u-boot]
Signed-off-by: Sean Anderson <seanga2@gmail.com>
1 file changed