docs: Fix conf.py for Sphinx 2.0

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.

Cc: stable@vger.kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/conf.py

@@ -37,7 +37,7 @@
 extensions = ['kerneldoc', 'rstFlatTable', 'kernel_include', 'cdomain', 'kfigure', 'sphinx.ext.ifconfig']
 
 # The name of the math extension changed on Sphinx 1.4
-if major == 1 and minor > 3:
+if (major == 1 and minor > 3) or (major > 1):
     extensions.append("sphinx.ext.imgmath")
 else:
     extensions.append("sphinx.ext.pngmath")