Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/lib/test_hash.c b/lib/test_hash.c
index cac20c5..0ee40b4 100644
--- a/lib/test_hash.c
+++ b/lib/test_hash.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * Test cases for <linux/hash.h> and <linux/stringhash.h>
  * This just verifies that various ways of computing a hash