Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/fs/xfs/xfs_bmap_util.h b/fs/xfs/xfs_bmap_util.h
index 87363d1..7a78229 100644
--- a/fs/xfs/xfs_bmap_util.h
+++ b/fs/xfs/xfs_bmap_util.h
@@ -80,4 +80,7 @@
 			  int whichfork, xfs_extnum_t *nextents,
 			  xfs_filblks_t *count);
 
+int	xfs_flush_unmap_range(struct xfs_inode *ip, xfs_off_t offset,
+			      xfs_off_t len);
+
 #endif	/* __XFS_BMAP_UTIL_H__ */