Add SPDX GPL-2.0+ to all PCI files that specified the GPL and allowed
either GPL version 2 or any later version.

Remove the boilerplate GPL version 2 or later language, relying on the
assertion in b2441318 ("License cleanup: add SPDX GPL-2.0 license
identifier to files with no license") that the SPDX identifier may be used
instead of the full boilerplate text.
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>