asoc: Update file header to GPL-2.0-only

Update file header to GPL-2.0-only.

Change-Id: Ic1542a3209a5fe73c937a5b36491ede4a451936d
Signed-off-by: Meng Wang <mengw@codeaurora.org>
diff --git a/asoc/codecs/wsa881x-registers.h b/asoc/codecs/wsa881x-registers.h
index c39edef..6e19b32 100644
--- a/asoc/codecs/wsa881x-registers.h
+++ b/asoc/codecs/wsa881x-registers.h
@@ -1,4 +1,4 @@
-/* SPDX-License-Identifier: GPL-2.0 */
+/* SPDX-License-Identifier: GPL-2.0-only */
 /* Copyright (c) 2015, The Linux Foundation. All rights reserved.
  */