fix(lts): static checks to point to lts

Changing references in static checks script from origin/master to
origin/lts-v2.8

Signed-off-by: Lauren Wehrmeister <lauren.wehrmeister@arm.com>
Change-Id: Ib954b64df2520e375a2479d7b04ee0a8083f2867
diff --git a/script/static-checks/check-copyright.py b/script/static-checks/check-copyright.py
index a05b4ca..509f889 100755
--- a/script/static-checks/check-copyright.py
+++ b/script/static-checks/check-copyright.py
@@ -180,7 +180,7 @@
 only files that are modified by the latest patch(es).""",
                         action="store_true")
 
-    (rc, stdout, stderr) = utils.shell_command(['git', 'merge-base', 'HEAD', 'refs/remotes/origin/master'])
+    (rc, stdout, stderr) = utils.shell_command(['git', 'merge-base', 'HEAD', 'refs/remotes/origin/lts-v2.8'])
     if rc:
         print("Git merge-base command failed. Cannot determine base commit.")
         sys.exit(rc)