rstp: Fix copyright year of rstp

Change copyright year from 2019,2020 to 2019-2020.

Signed-off-by: Tian Yang <tiany@codeaurora.org>
Change-Id: I5d9ba82175c62e669f977de28449e0cf264a39d1

rstp/files/lib/functions/rstp.sh

 #!/bin/sh
 
-# Copyright (c) 2013, 2017, 2019, 2020 The Linux Foundation. All rights reserved.
+# Copyright (c) 2013, 2017, 2019-2020 The Linux Foundation. All rights reserved.
 #
 # Permission to use, copy, modify, and/or distribute this software for any
 # purpose with or without fee is hereby granted, provided that the above