files-reg: Revert: Make try_clean_ghost() use struct ghost_file ptr

ghost_files populates another process, than who does try_clean_ghost(),
so this list is not visible for the cleaner. Revert the patch.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>