vfio/pci: Cleanup license mess

The recently added nvlink2 VFIO driver introduced a license conflict in two
files. In both cases the SPDX license identifier is:

  SPDX-License-Identifier: GPL-2.0+

but the files contain also the following license boiler plate text:

  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation

The latter is GPL-2.9-only and not GPL-2.0=.

Looking deeper. The nvlink source file is derived from vfio_pci_igd.c which
is also licensed under GPL-2.0-only and it can be assumed that the file was
copied and modified. As the original file is licensed GPL-2.0-only it's not
possible to relicense derivative work to GPL-2.0-or-later.

Fix the SPDX identifier and remove the boiler plate as it is redundant.

Fixes: 7f928917 ("vfio_pci: Add NVIDIA GV100GL [Tesla V100 SXM2] subdriver")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: kvm@vger.kernel.org
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/pci/trace.h

-/* SPDX-License-Identifier: GPL-2.0+ */
+/* SPDX-License-Identifier: GPL-2.0-only */
 /*
  * VFIO PCI mmap/mmap_fault tracepoints
  *
  * Copyright (C) 2018 IBM Corp.  All rights reserved.
  *     Author: Alexey Kardashevskiy <aik@ozlabs.ru>
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
  */
 
 #undef TRACE_SYSTEM

drivers/vfio/pci/vfio_pci_nvlink2.c

-// SPDX-License-Identifier: GPL-2.0+
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * VFIO PCI NVIDIA Whitherspoon GPU support a.k.a. NVLink2.
  *
  * Copyright (C) 2018 IBM Corp.  All rights reserved.
  *     Author: Alexey Kardashevskiy <aik@ozlabs.ru>
  *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- *
  * Register an on-GPU RAM region for cacheable access.
  *
  * Derived from original vfio_pci_igd.c: