sched/core_ctl: Refactor cpu data

Refactor cpu data into cpu data and cluster data to improve readability and
ease of understanding the code.

Change-Id: I63c7488a68ec6005376e2f1bff20d765903115f7
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>