Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/um/include/asm/pgtable-3level.h b/arch/um/include/asm/pgtable-3level.h
index c4d876d..9812269 100644
--- a/arch/um/include/asm/pgtable-3level.h
+++ b/arch/um/include/asm/pgtable-3level.h
@@ -1,7 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Copyright 2003 PathScale Inc
  * Derived from include/asm-i386/pgtable.h
- * Licensed under the GPL
  */
 
 #ifndef __UM_PGTABLE_3LEVEL_H