Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/lib/zlib_deflate/Makefile b/lib/zlib_deflate/Makefile
index 86275e3..2622e03 100644
--- a/lib/zlib_deflate/Makefile
+++ b/lib/zlib_deflate/Makefile
@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
 #
 # This is a modified version of zlib, which does all memory
 # allocation ahead of time.
diff --git a/lib/zlib_deflate/deflate_syms.c b/lib/zlib_deflate/deflate_syms.c
index ccfe25f..72fe4b7 100644
--- a/lib/zlib_deflate/deflate_syms.c
+++ b/lib/zlib_deflate/deflate_syms.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * linux/lib/zlib_deflate/deflate_syms.c
  *