Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/arm/net/Makefile b/arch/arm/net/Makefile
index c2c1084..3354b3e 100644
--- a/arch/arm/net/Makefile
+++ b/arch/arm/net/Makefile
@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
 # ARM-specific networking code
 
 obj-$(CONFIG_BPF_JIT) += bpf_jit_32.o