Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/tools/bpf/bpf_asm.c b/tools/bpf/bpf_asm.c
index c15aef0..e5f95e3 100644
--- a/tools/bpf/bpf_asm.c
+++ b/tools/bpf/bpf_asm.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * Minimal BPF assembler
  *
@@ -16,7 +17,6 @@
  *    pretty print a C-like construct.
  *
  * Copyright 2013 Daniel Borkmann <borkmann@redhat.com>
- * Licensed under the GNU General Public License, version 2.0 (GPLv2)
  */
 
 #include <stdbool.h>