sched: avoid running idle_balance() on behalf of wrong CPU

With EA (Energy Awareness), idle_balance() on a CPU runs on behalf of most
power efficient idle CPU among the CPUs in its sched domain level under the
condition that the substitute idle CPU should be limited to a CPU which has
the same capacity with original idle CPU.
It is found that at present idle_balance() spans all the CPUs in its sched
domain and run idle balancer on behalf of any CPU within the domain which
could be all the CPUs in the system which consequently makes idle balancer
on a performance CPU always runs on behalf of a power efficient idle CPU.
This would cause for idle performance CPUs to fail to pull tasks from power
efficient CPUs always when there is only an online performance CPU.

Limit search CPUs to cache sharing CPUs with original idle CPU to ensure to
run idle balancre on behalf of more power efficient CPU but still has the
same capacity with original CPU to fix such issue.

Change-Id: I0575290c24f28db011d9353915186e64df7e57fe
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>