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/msm-pcm-routing-devdep.c b/asoc/msm-pcm-routing-devdep.c
index 6d26c54..cddc2a1 100644
--- a/asoc/msm-pcm-routing-devdep.c
+++ b/asoc/msm-pcm-routing-devdep.c
@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0-only
 /* Copyright (c) 2014, 2016-2017 The Linux Foundation. All rights reserved.
  */