bpf: Add SPDX license identifiers to a few files

Add GPL-2.0 SPDX-License-Identifier lines to some files,
and remove a reference to COPYING, and boilerplate warranty
text, from offload.c.

Signed-off-by: Tim Bird <tim.bird@sony.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260115013129.598705-1-tim.bird@sony.com

kernel/bpf/offload.c

@@ -1,16 +1,6 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2017-2018 Netronome Systems, Inc.
- *
- * This software is licensed under the GNU General License Version 2,
- * June 1991 as shown in the file COPYING in the top-level directory of this
- * source tree.
- *
- * THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS"
- * WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING,
- * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
- * FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE
- * OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME
- * THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
  */
 
 #include <linux/bpf.h>

kernel/bpf/ringbuf.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 #include <linux/bpf.h>
 #include <linux/btf.h>
 #include <linux/err.h>

kernel/bpf/token.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 #include <linux/bpf.h>
 #include <linux/vmalloc.h>
 #include <linux/file.h>