ANDROID: sched/fair: prevent meaningless active migration

At present need_active_balance() determines whether an active
upmigration is needed by using capacity_of(). A CPU's capacity
may be reduced by RT pressure, and therefore distinguishing
capability differences with capacity_of() may lead to suboptimal
active migrations to less capable CPUs. Use capacity_orig_of
to distinguish differently capable CPUs in addition to
capacity_of(), thus avoiding placing tasks on less capable CPUs
due to instantaneous RT pressure.

Change-Id: I3e1435246a8edc3ad618ef98a34866cfbd8c16a5
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>
[markivx: Reworked the commit text a bit]
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>
(cherry picked from commit 7ab48e4c8d9e0652bd978f3df26c29e64b5ea85a)
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
Signed-off-by: Chris Redpath <chris.redpath@arm.com>