Add tf-m-tests dependency to cppcheck

Change-Id: I7a22c71bc5632feb4b613ef461e1c69430d804d7
Signed-off-by: Kevin Peng <kevin.peng@arm.com>
diff --git a/jenkins/cppcheck.jpl b/jenkins/cppcheck.jpl
index 872a0d9..34e23b1 100644
--- a/jenkins/cppcheck.jpl
+++ b/jenkins/cppcheck.jpl
@@ -56,6 +56,20 @@
         ]
       )
     }
+    dir("tf-m-tests") {
+      checkout(
+        changelog: false,
+        poll: false,
+        scm: [
+          $class: 'GitSCM',
+          branches: [[name: 'FETCH_HEAD']],
+          userRemoteConfigs: [[
+            refspec: '$TFM_TESTS_REFSPEC',
+            url: params.TFM_TESTS_URL
+          ]]
+        ]
+      )
+    }
     sh """
     # Host https://github.com/Arm-software/CMSIS_5/releases/download/5.5.0/ARM.CMSIS.5.5.0.pack
     # under \$JENKINS_HOME/userContent