Fix extraction of a ranged type's maximum value in policy generator.

BUG=None
R=ljusten@chromium.org

Change-Id: I0c0f6e061c5d81e0d823d155b84dbf887867bbde
Reviewed-on: https://chromium-review.googlesource.com/889499Reviewed-by: Lutz Justen <ljusten@chromium.org>
Commit-Queue: Greg Thompson <grt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532403}

components/policy/tools/generate_policy_source.py

@@ -518,7 +518,7 @@ class SchemaNodesGenerator:
       min_value = int(schema['minimum'])
       min_value_set = True
     if 'maximum' in schema:
-      max_value = int(schema['minimum'])
+      max_value = int(schema['maximum'])
       max_value_set = True
     if min_value_set and max_value_set and min_value > max_value:
       raise RuntimeError('Invalid ranged type in %s' % name)