x86/kvmclock: convert to SPDX identifiers

Update the verbose license text with the matching SPDX
license identifier.
Signed-off-by: Peng Hao <peng.hao2@zte.com.cn>
[Changed deprecated GPL-2.0+ to GPL-2.0-or-later. - Radim]
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

arch/x86/kernel/kvmclock.c

+// SPDX-License-Identifier: GPL-2.0-or-later
 /*  KVM paravirtual clock driver. A clocksource implementation
     Copyright (C) 2008 Glauber de Oliveira Costa, Red Hat Inc.
-
-    This program is free software; you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation; either version 2 of the License, or
-    (at your option) any later version.
-
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
-
-    You should have received a copy of the GNU General Public License
-    along with this program; if not, write to the Free Software
-    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
 
 #include <linux/clocksource.h>