fsi: cf-fsi-fw: Use the correct style for SPDX License Identifier

This patch corrects the SPDX License Identifier style
in header file related to Drivers for FRU Support Interface.
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/2019/2/7/46Suggested-by: Joe Perches <joe@perches.com>
Signed-off-by: Nishad Kamdar <nishadkamdar@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/fsi/cf-fsi-fw.h

-// SPDX-License-Identifier: GPL-2.0+
+/* SPDX-License-Identifier: GPL-2.0+ */
 #ifndef __CF_FSI_FW_H
 #define __CF_FSI_FW_H