Coverity: Enable manually setting CI repo configs

To make it more convenient for users to manually trigger coverity job
for different use cases, enable manually setting CI repo related configs
in Jenkins.

Signed-off-by: Xinyu Zhang <xinyu.zhang@arm.com>
Change-Id: I66adfefc8faea067e53e16f5bed876d77c21b2d1
diff --git a/tf-m-coverity.yaml b/tf-m-coverity.yaml
index e1b8385..9865872 100644
--- a/tf-m-coverity.yaml
+++ b/tf-m-coverity.yaml
@@ -9,11 +9,9 @@
     name: tf-m-ci-scripts
     scm:
         - git:
-            url: https://git.trustedfirmware.org/ci/tf-m-ci-scripts.git
-            refspec: +refs/heads/main:refs/remotes/origin/master
-            name: origin
+            url: ${CI_SCRIPTS_REPO}
             branches:
-                - refs/heads/main
+                - ${CI_SCRIPTS_BRANCH}
             basedir: tf-m-ci-scripts
             skip-tag: true
             shallow-clone: true