Comment 1 for bug 2051924

Commit "eventfs: Do not allow NULL parent to eventfs_start_creating()" had to be dropped.
This introduced a warning: "WARNING: CPU: 17 PID: 1 at fs/tracefs/inode.c:408 start_creating+0xe9/0x110" that can be seen during boot testing. The check itself would not be an issue, but the commit was removes the following in start_creating:
```
- /* If the parent is not specified, we create it in the root.
- * We need the root dentry to do this, which is in the super
- * block. A pointer to that is in the struct vfsmount that we
- * have around.
- */
- if (!parent)
- parent = tracefs_mount->mnt_root;
-
```
This is used a lot for entries that are created in the root directory, therefore these entries cannot be created anymore.

```
root@mantic:/home/ubuntu# ll /sys/kernel/tracing/
total 0
drwx------ 2 root root 0 Mar 7 14:29 ./
drwxr-xr-x 16 root root 0 Mar 7 14:29 ../
```

I would keep the warning entry, but this would create a bit of confusion because we'll deviate from upstream. Therefore, I'll drop the commit