mm: oom_kill: switch test-and-clear of known TIF_MEMDIE to clear

mm: oom_kill: switch test-and-clear of known TIF_MEMDIE to clear

exit_oom_victim() already knows that TIF_MEMDIE is set, and nobody else
can clear it concurrently.  Use clear_thread_flag() directly.

Signed-off-by: Johannes Weiner <[email protected]>
Acked-by: David Rientjes <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Tetsuo Handa <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Dave Chinner <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>