crypto: cavium/nitrox - Use the correct style for SPDX License Identifier

This patch corrects the SPDX License Identifier style
in header files related to Crypto Drivers for Cavium Nitrox
family CNN55XX devices.
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: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/cavium/nitrox/nitrox_debugfs.h

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

drivers/crypto/cavium/nitrox/nitrox_mbx.h

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