mm/memory-failure.c: cleanup in unpoison_memory

mm/memory-failure.c: cleanup in unpoison_memory

If freeit is true, the value of ret must be zero, there is no need to
check the value of freeit after label unlock_mutex.

We can drop variable freeit to do this cleanup.

Link: https://lkml.kernel.org/r/20221125065444.3462681-1-mawupeng1@huawei.com
Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: zhenwei pi <pizhenwei@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>