zram: clear IDLE flag in mark_idle()

If entry does not fulfill current mark_idle() parameters, e.g.  cutoff
time, then we should clear its ZRAM_IDLE from previous mark_idle()
invocations.

Consider the following case:
- mark_idle() cutoff time 8h
- mark_idle() cutoff time 4h
- writeback() idle - will writeback entries with cutoff time 8h,
  while it should only pick entries with cutoff time 4h

The bug was reported by Shin Kawamura.

Link: https://lkml.kernel.org/r/20241028153629.1479791-3-senozhatsky@chromium.org


Fixes: 755804d1 ("zram: introduce an aged idle interface")
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reported-by: Shin Kawamura <kawasin@google.com>
Acked-by: Brian Geffon <bgeffon@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: <stable@vger.kernel.org>