Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/xtensa/include/asm/pgtable.h b/arch/xtensa/include/asm/pgtable.h
index 29cfe42..3f7fe5a 100644
--- a/arch/xtensa/include/asm/pgtable.h
+++ b/arch/xtensa/include/asm/pgtable.h
@@ -1,10 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
 /*
  * include/asm-xtensa/pgtable.h
  *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- *
  * Copyright (C) 2001 - 2013 Tensilica Inc.
  */
 
@@ -241,7 +238,6 @@
 # define swapper_pg_dir NULL
 static inline void paging_init(void) { }
 #endif
-static inline void pgtable_cache_init(void) { }
 
 /*
  * The pmd contains the kernel virtual address of the pte page.