base-files: bump Copyright to 2021

This commit is only added to keep the PKG_RELEASE correct after fixing
the $(COMMITCOUNT) logic in the previous commit.

This way the PKG_RELEASE stays the same while the compiled packages
content isn't changed.

Signed-off-by: Paul Spooren <[email protected]>

package/base-files/Makefile

@@ -1,5 +1,5 @@
 #
-# Copyright (C) 2007-2016 OpenWrt.org
+# Copyright (C) 2007-2021 OpenWrt.org
 # Copyright (C) 2010 Vertical Communications
 #
 # This is free software, licensed under the GNU General Public License v2.