mm: fix oom killing for disabled pid

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I46IUJ


CVE: NA

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In oom_next_task(), if points is equal to LONG_MIN, then we choose it to
kill. That is not correct. LONG_MIN means to disable killing it. So fix
it.

Fixes: 4da32073 ("memcg: support priority for oom")
Signed-off-by: Jing Xiangfeng <jingxiangfeng@huawei.com>
Reviewed-by: Chen Wandun <chenwandun@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>