ASoC: switch audio drivers to SPDX identifier

Switch audio drivers to SPDX identifier on msm-4.19.

Change-Id: Ic3f0230a516db251b8d81e8a7e73dbc04d66fe1b
Signed-off-by: Meng Wang <mengw@codeaurora.org>

asoc/machine_815x_init.c

@@ -1,16 +1,7 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
-Copyright (c) 2017-2018, The Linux Foundation. All rights reserved.
-
-This program is free software; you can redistribute it and/or modify
-it under the terms of the GNU General Public License version 2 and
-only version 2 as published by the Free Software Foundation.
-
-This program is distributed in the hope that it will be useful,
-but WITHOUT ANY WARRANTY; without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-GNU General Public License for more details.
-*
-*/
+ * Copyright (c) 2017-2018, The Linux Foundation. All rights reserved.
+ */
 
 #include <linux/kernel.h>
 #include <linux/module.h>