btrfs: tree-log.c: Wrong printk information about namelen

In verify_dir_item, it wants to printk name_len of dir_item but
printk data_len acutally.

Fix it by calling btrfs_dir_name_len instead of btrfs_dir_data_len.
Signed-off-by: NSu Yue <suy.fnst@cn.fujitsu.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NChris Mason <clm@fb.com>

fs/btrfs/dir-item.c

@@ -468,7 +468,7 @@ int verify_dir_item(struct btrfs_fs_info *fs_info,
 
 	if (btrfs_dir_name_len(leaf, dir_item) > namelen) {
 		btrfs_crit(fs_info, "invalid dir item name len: %u",
-		       (unsigned)btrfs_dir_data_len(leaf, dir_item));
+		       (unsigned)btrfs_dir_name_len(leaf, dir_item));
 		return 1;
 	}