sched: Add CONFIG_SCHED_HMP Kconfig option

Add a compile-time flag to enable or disable scheduler features for
HMP (heterogenous multi-processor) systems. Main feature deals with
optimizing task placement for best power/performance tradeoff.

Also extend features currently dependent on CONFIG_SCHED_FREQ_INPUT to
be enabled for CONFIG_HMP as well.

Change-Id: I03b3942709a80cc19f7b934a8089e1d84c14d72d
Signed-off-by: Srivatsa Vaddagiri <vatsa@codeaurora.org>