subject of the patch: ubifs: Fix ubifs_tnc_lookup() usage in do_kill_orphans()

the commit ID: 4ab25ac8b2b5514151d5f91cf9514df08dd26938

why you think it should be applied: I ran into the problem fixed by this patch on linux-5.4.28-rt19. After applying this patch to my internal tree, the problem was solved.

and what kernel version you wish it to be applied to. linux-5.4.y (tested by me) and maybe others