drm_hwcomposer: Add commit message validation to CI

Check the subject prefix starts with "drm_hwcomposer: " and we have
Signed-off-by tags for both author and committer.

Change-Id: Ib26b8e5cbeae2156014f2bbfb8703545bdc1decb
Signed-off-by: Sean Paul <seanpaul@chromium.org>
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index d0175f0..c97f4ff 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -12,5 +12,4 @@
   script: "./.gitlab-ci-checkcommit.sh"
   artifacts:
     when: on_failure
-    paths:
-      - format-fixup.patch
+    untracked: true