qcacmn: Fix copyright

Fix modified year in the copyright banner.

CRs-Fixed: 3036102
Change-Id: I97c39555e7e24ed8b12687983d19f418234bd614

qdf/inc/qdf_list.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014-2021 The Linux Foundation. All rights reserved.
+ * Copyright (c) 2014-2018, 2021 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