reiserfs: change j_timestamp type to time64_t

This uses the deprecated time_t type but is write-only, and could be
removed, but as Jeff explains, having a timestamp can be usefule for
post-mortem analysis in crash dumps.

In order to remove one of the last instances of time_t, this changes the
type to time64_t, same as j_trans_start_time.

Link: http://lkml.kernel.org/r/20180622133315.221210-1-arnd@arndb.deSigned-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Jan Kara <jack@suse.cz>
Cc: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/reiserfs/reiserfs.h

@@ -271,7 +271,7 @@ struct reiserfs_journal_list {
 
 	struct mutex j_commit_mutex;
 	unsigned int j_trans_id;
-	time_t j_timestamp;
+	time64_t j_timestamp; /* write-only but useful for crash dump analysis */
 	struct reiserfs_list_bitmap *j_list_bitmap;
 	struct buffer_head *j_commit_bh;	/* commit buffer head */
 	struct reiserfs_journal_cnode *j_realblock;