sched: energy: calculate and update CPU capacity dynamically

One SoC can have multiple CPU speedbins which cannot be represented
with current energy model due to fixed capacity per CPU frequency
steps.

Provide CPU's all possible frequency steps instead of capacities along
with corresponding energy costs to be able to support different
speedbins.

Change-Id: I96ff01372da5c383cd3172999ea1dcf95a7862ce
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>