sched/fair: Provide can_migrate_task_llc

maillist inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8PIYZ
CVE: NA

Reference: https://lore.kernel.org/lkml/1541767840-93588-8-git-send-email-steven.sistare@oracle.com/



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Define a simpler version of can_migrate_task called can_migrate_task_llc
which does not require a struct lb_env argument, and judges whether a
migration from one CPU to another within the same LLC should be allowed.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Signed-off-by: Cheng Yu <serein.chengyu@huawei.com>