media: fix SPDX comment on some header files

The agreed format is to use /* */ comments inside header
files. Unfortunately, I ended by using // on a few ones.

Reported-by: Andi Shyti <andi.shyti@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/rc/rc-core-priv.h

@@ -1,7 +1,9 @@
-// SPDX-License-Identifier: GPL-2.0
-// Remote Controller core raw events header
-//
-// Copyright (C) 2010 by Mauro Carvalho Chehab
+/*
+ * SPDX-License-Identifier: GPL-2.0
+ * Remote Controller core raw events header
+ *
+ * Copyright (C) 2010 by Mauro Carvalho Chehab
+ */
 
 #ifndef _RC_CORE_PRIV
 #define _RC_CORE_PRIV