sched/fair: Add sched_compute_energy trace point

Add sched_compute_energy trace point to aid the task placement
issues debugging. It prints the energy of all the evaluated
CPUs and the best_energy for each iteration.

Change-Id: I965a950de5006bdc601a9fcc146d8d619409dd8f
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>