sched/fair: Don't assume higher capacity means higher power

Apply the load balancer restrictions based on the power
instead of capacity. There is no change in behavior for
a big.LITTLE system on which higher capacity means higher
power.

Change-Id: Ia4d4ad7deb9e26e6e41033f53555fb6b1aca59b9
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>