sched: provide per cpu-cgroup option to notify on migrations

On systems where CPUs may run asynchronously, task migrations
between CPUs running at grossly different speeds can cause
problems.
This change provides a mechanism to notify a subsystem
in the kernel if a task in a particular cgroup migrates to a
different CPU. Other subsystems (such as cpufreq) may then
register for this notifier to take appropriate action when
such a task is migrated.
The cgroup attribute to set for this behavior is
"notify_on_migrate" .
Change-Id: Ie1868249e53ef901b89c837fdc33b0ad0c0a4590
Signed-off-by: Steve Muckle <smuckle@codeaurora.org>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>