etmem: add ETMEM scan feature CONFIG to mm/Kconfig

euleros inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8T1MB?from=project-issue


CVE: NA

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etmem scan is a critical part of the etmem feature.
A kernel module, etmem_scan.ko periodically scans the appointed vma
segments of the target process, perform page table walk accordingly,
check and clear the access bit of each page before finally report
scan results back to user space.

Signed-off-by: Yuchen Tang <tangyuchen5@huawei.com>