sched: add option whether CPU C-state is used to guide task placement

There are CPUs that don't have an obvious low power mode exit latency
penalty.  Add a new Kconfig CONFIG_SCHED_HMP_CSTATE_AWARE which controls
whether CPU C-state is used to guide task placement.

CRs-fixed: 1006303
Change-Id: Ie8dbab8e173c3a1842d922f4d1fbd8cc4221789c
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>