provide cgroup option to notify on migrations

    backported to 3.0 from:

    1) 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"

    Signed-off-by: Steve Muckle <smuckle@codeaurora.org>
    =====

    2) sched: remove migration notification from RT class

    Commit "sched: provide per cpu-cgroup option to notify on migrations"added
    a notifier call when a task is moved to a different CPU.
    Unfortunately the two call sites in the RT sched class where this occurs
    happens with a runqueue lock held.
    This can result in a deadlock if the notifier call
    attempts to do something like wake up a task.
    Fortunately the benefit of that change comes mainly
    from notifying on migration of non-RT tasks,
    so we can simply ignore the movements of RT tasks.

    CRs-Fixed: 491370
    Signed-off-by: Steve Muckle <smuckle@codeaurora.org>
    =====

    Change-Id: I2e84ae0c41bd544231924ff25cbf14d88e008fed

Change-Id: I02a73c69356661f2aeae17fd5b037d44c266ae94