Update message for psdk -s

Previous message was confusing as if -s would overwrite the
configuration file found on the persistent storage. This patch improves
the message.

Signed-off-by: Peter Senna Tschudin <peter.senna@collabora.com>

tools/psdk

@@ -420,7 +420,7 @@ def persistent_to_conf(persistent_conf_file):
     command = ["sudo", "ln", "-sf", persistent_conf_file, conf_file]
     _run(command)
 
-    print("Configuration file moved to persistent storage. From now on, " +\
+    print("Using configuration file found on persistent storage. From now on, " +\
           "changes made to {} will be saved on the persistent storage.".format(conf_file))
 
 def scan_persistent_etc():