tf-a-commitlint: add commitlint job

commitlint is being introduced into the TF-A prerequisites, and will
dictate the style of commit messages going into the project. This job
runs commitlint to validate commit messages between a given commit and
its merge base, and is triggered by the Gerrit level one job.

Presently, this job will only verify patches that have been submitted
by @arm.com addresses. This will be rolled out to everybody upon the
next release.

Signed-off-by: Chris Kay <chris.kay@arm.com>
Change-Id: I6c81dd60c97afa07ff1e80ed968b7ac896099912
diff --git a/tf-gerrit-tforg-l1.yaml b/tf-gerrit-tforg-l1.yaml
index 083a634..c85ff71 100644
--- a/tf-gerrit-tforg-l1.yaml
+++ b/tf-gerrit-tforg-l1.yaml
@@ -56,6 +56,16 @@
         TF_GERRIT_REFSPEC=${GERRIT_REFSPEC}
         EOF
     - multijob:
+        name: Lint commit messages
+        condition: COMPLETED
+        projects:
+        - name: tf-a-commitlint
+          kill-phase-on: NEVER
+          predefined-parameters: |
+            REFSPEC=${GERRIT_REFSPEC}
+            REFNAME=${GERRIT_BRANCH}
+            REFNAME_BASE=origin/integration
+    - multijob:
         condition: COMPLETED
         name: Build and static checks
         projects: