Sanitize qnx4 fsync handling

* have directory operations use mark_buffer_dirty_inode(),
  so that sync_mapping_buffers() would get those.
* make qnx4_write_inode() honour its last argument.
* get rid of insane copies of very ancient "walk the indirect blocks"
  in qnx4/fsync - they never matched the actual fs layout and, fortunately,
  never'd been called.  Again, all this junk is not needed; ->fsync()
  should just do sync_mapping_buffers + sync_inode (and if we implement
  block allocation for qnx4, we'll need to use mark_buffer_dirty_inode()
  for extent blocks)

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/qnx4/dir.c b/fs/qnx4/dir.c
index ea9ffef..ff6c1ba 100644
--- a/fs/qnx4/dir.c
+++ b/fs/qnx4/dir.c
@@ -84,7 +84,7 @@
 {
 	.read		= generic_read_dir,
 	.readdir	= qnx4_readdir,
-	.fsync		= file_fsync,
+	.fsync		= simple_fsync,
 };
 
 const struct inode_operations qnx4_dir_inode_operations =