zsmalloc: remove zs_compact_control

__zs_compact always putback src_zspage into class list after
migrate_zspage.  Thus, we don't need to keep last position of src_zspage
any more.  Let's remove it.

Link: https://lkml.kernel.org/r/20230624053120.643409-4-senozhatsky@chromium.org


Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Alexey Romanov <avromanov@sberdevices.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>