mm: introduce "clear_freelist" kernel parameter

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4XB9H


CVE: NA

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CONFIG_CLEAR_FREELIST_PAGE specifies the default value for clear
freelist. Add a kernel parameter to make it possible to
override the default. Keep clear_freelist disabled unless
"clear_freelist" is explicitly specified.

Signed-off-by: Yu Liao <liaoyu15@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Laibin Qiu <qiulaibin@huawei.com>