ANDROID: sched: Per-Sched-domain over utilization

The current implementation of overutilization, aborts energy aware
scheduling if any cpu in the system is over-utilized. This patch introduces
over utilization flag per sched domain level instead of a single flag
system wide.  Load balancing is done at the sched domain where any
of the cpu is over utilized. If energy aware scheduling is
enabled and no cpu in a sched domain is overuttilized,
load balancing is skipped for that sched domain and energy aware
scheduling continues at that level.

The implementation takes advantage of the shared sched_domain structure
that is common across all the sched domains at a level. The new flag
introduced is placed in this structure so that all the sched domains the
same level share the flag. In case of an overutilized cpu, the flag gets
set at level1 sched_domain. The flag at the parent sched_domain level gets
set in either of the two following scenarios.
 1. There is a misfit task in one of the cpu's in this sched_domain.
 2. The total utilization of the domain is greater than the domain capacity

The flag is cleared if no cpu in a sched domain is overutilized.

This implementation still can have corner scenarios with respect to
misfit tasks. For example consider a sched group with n cpus and
n+1 70%utilized tasks. Ideally this is a case for load balance to happen
in a parent sched domain. But neither the total group utilization is
high enough for the load balance to be triggered
in the parent domain nor there is a cpu with a single overutilized task so
that aload balance is triggered in a parent domain. But again this could be
a purely academic sceanrio, as during task wake up these tasks will be placed
more appropriately.

Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>
Change-Id: I3f327cff4080096a3e58208dd72c9b7f7913cdb2
Signed-off-by: Chris Redpath <chris.redpath@arm.com>
Git-commit: addef378
Git-repo: https://android.googlesource.com/kernel/common/


[satyap@codeaurora.org: trivial merge conflict resolution]
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>