media: tuners: Use the correct style for SPDX License Identifier

This patch corrects the SPDX License Identifier style
in header file related to media Drivers for Analog TV Tuners.
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: Sean Young <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/tuners/tuner-xc2028-types.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
- * SPDX-License-Identifier: GPL-2.0
  * tuner-xc2028_types
  *
  * This file includes internal tipes to be used inside tuner-xc2028.

drivers/media/tuners/tuner-xc2028.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
- * SPDX-License-Identifier: GPL-2.0
  * tuner-xc2028
  *
  * Copyright (c) 2007-2008 Mauro Carvalho Chehab <[e-mail]>