jenkins/: Use tfgit.checkout_ci_scripts()

Consistently use single function for clone tf-m-ci-scripts repo with
parameters defined by job (e.g. specifying a change reference to fetch).

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I76eb4c6c31633b98489f82d29015c7d9486418ff
diff --git a/jenkins/lava-submit.jpl b/jenkins/lava-submit.jpl
index 631a6c8..5103d31 100644
--- a/jenkins/lava-submit.jpl
+++ b/jenkins/lava-submit.jpl
@@ -6,6 +6,9 @@
 //
 //-------------------------------------------------------------------------------
 
+@Library('trustedfirmware') _
+
+
 @NonCPS
 def isPerPatchJob() {
   def upstream_job = manager.build.getAction(hudson.model.CauseAction.class).getCauses()[0]
@@ -64,7 +67,7 @@
     stage("Init") {
       cleanWs()
       dir("tf-m-ci-scripts") {
-        checkout([$class: 'GitSCM', branches: [[name: '$CI_SCRIPTS_BRANCH']], userRemoteConfigs: [[credentialsId: 'GIT_SSH_KEY', url: '$CI_SCRIPTS_REPO']]])
+        tfgit.checkout_ci_scripts()
         withCredentials([string(credentialsId: 'TUXSUITE_TOKEN', variable: 'TUXSUITE_TOKEN')]) {
           sh "jenkins/tuxsuite-setup.sh"
         }