powerpc: Use the correct style for SPDX License Identifier

This patch corrects the SPDX License Identifier style
in the powerpc Hardware Architecture related files.
Suggested-by: NJoe Perches <joe@perches.com>
Signed-off-by: NNishad Kamdar <nishadkamdar@gmail.com>
Acked-by: NAndrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/pnv-ocxl.h

-// SPDX-License-Identifier: GPL-2.0+
+/* SPDX-License-Identifier: GPL-2.0+ */
 // Copyright 2017 IBM Corp.
 #ifndef _ASM_PNV_OCXL_H
 #define _ASM_PNV_OCXL_H