anv: use cElementTree in anv_entrypoints_gen.py

It's written in C rather than pure python and is strictly faster, the
only reason not to use it that it's classes cannot be subclassed.

Signed-off-by: Dylan Baker <dylanx.c.baker@intel.com>

src/intel/vulkan/anv_entrypoints_gen.py

@@ -26,7 +26,7 @@ import argparse
 import functools
 import os
 import textwrap
-import xml.etree.ElementTree as et
+import xml.etree.cElementTree as et
 
 from mako.template import Template