CPP-Check: Set Head of Master Branch of TF-M as Default

Change-Id: I1a46906db17a77e6ecaf34a122ad48d06906c7b1
Signed-off-by: Xinyu Zhang <xinyu.zhang@arm.com>
diff --git a/tf-m-cppcheck.yaml b/tf-m-cppcheck.yaml
index c989be6..8303a88 100644
--- a/tf-m-cppcheck.yaml
+++ b/tf-m-cppcheck.yaml
@@ -27,7 +27,7 @@
             For use when triggering with unmerged Gerrit changes.
       - string:
           name: 'GERRIT_REFSPEC'
-          default: '+refs/heads/*:refs/remotes/origin/*'
+          default: 'refs/heads/master'
           description: |
             For use when triggering with unmerged Gerrit changes.
       - string: