staging: fsl-dpaa2: fix SPDX identifiers in header files

Use the correct comment style for SPDX identifiers in header files.
Reported by checkpatch.
Signed-off-by: Michael Straube <straube.linux@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/fsl-dpaa2/ethsw/dpsw-cmd.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Copyright 2014-2016 Freescale Semiconductor Inc.
  * Copyright 2017-2018 NXP

drivers/staging/fsl-dpaa2/ethsw/dpsw.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Copyright 2014-2016 Freescale Semiconductor Inc.
  * Copyright 2017-2018 NXP

drivers/staging/fsl-dpaa2/ethsw/ethsw.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * DPAA2 Ethernet Switch declarations
  *