platform/x86: intel-ips: Use the correct style for SPDX License Identifier

This patch corrects the SPDX License Identifier style in
header files related to x86 Platform Specific Drivers.
For C header files Documentation/process/license-rules.rst
mandates C-like comments (opposed to C source files where
C++ style should be used).

Changes made by using a script provided by Joe Perches here:
https://lkml.org/lkml/2019/2/7/46.

Suggested-by: Joe Perches <[e-mail]>
Signed-off-by: Nishad Kamdar <[e-mail]>
Signed-off-by: Andy Shevchenko <[e-mail]>

drivers/platform/x86/intel_ips.h

···
-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Copyright (c) 2010 Intel Corporation
  */

drivers/platform/x86/intel_pmc_core.h

···
-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Intel Core SoC Power Management Controller Header File
  *