sched: Call init_sched_energy_costs() before sched_energy_probe()

There is no guarantee that init_sched_energy_costs() is completed before
sched_energy_probe() gets called. Make sure this happens.

While at it, do some code cleanup of unused code.

Change-Id: I4bd49f7c98dfafb9b794372259f19461900df857
Signed-off-by: Puja Gupta <pujag@codeaurora.org>