Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/fs/nfs_common/grace.c b/fs/nfs_common/grace.c
index 5be08f0..b73d9dd 100644
--- a/fs/nfs_common/grace.c
+++ b/fs/nfs_common/grace.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * Common code for control of lockd and nfsv4 grace periods.
  *