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>