mm/memory-failure.c: simplify num_poisoned_pages_inc/dec

mm/memory-failure.c: simplify num_poisoned_pages_inc/dec

Originally, do num_poisoned_pages_inc() in memory failure routine, use
num_poisoned_pages_dec() to rollback the number if filtered/ cancelled.

Suggested by Naoya, do num_poisoned_pages_inc() only in action_result(),
this make this clear and simple.

Link: https://lkml.kernel.org/r/20220509105641.491313-6-pizhenwei@bytedance.com
Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>