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>

asoc/codecs/wcd9xxx-soc-init.c

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright (c) 2017, The Linux Foundation. All rights reserved.
  */