sched: add power aware scheduling sysctl

The sched_enable_power_aware sysctl will control whether
or not scheduling decisions are influenced by the power
consumption of individual CPUs.

Change-Id: I312f892cf76a3fccc4ecc8aa6703908b205267f0
Signed-off-by: Steve Muckle <smuckle@codeaurora.org>
Signed-off-by: Srivatsa Vaddagiri <vatsa@codeaurora.org>