coverity_tf_conf.py: fix typo, missing comma in exclude_paths tuple

Signed-off-by: Fathi Boudra <fathi.boudra@linaro.org>
Change-Id: I350fc4f43be109fc24fda0d4b5a8315593862757
diff --git a/script/tf-coverity/coverity_tf_conf.py b/script/tf-coverity/coverity_tf_conf.py
index 2edc324..405f966 100644
--- a/script/tf-coverity/coverity_tf_conf.py
+++ b/script/tf-coverity/coverity_tf_conf.py
@@ -15,6 +15,6 @@
 # - description aims at providing the reason why the files are expected
 #   to be excluded.
 exclude_paths = [
-    ("platform/ext/.*", "3rd party libraries will not be fixed")
+    ("platform/ext/.*", "3rd party libraries will not be fixed"),
     ("lib/ext/.*", "3rd party libraries will not be fixed"),
 ]