sched: fair: Modify capacity margins for atoll

This is tuned to match energy model characteristics and scheduler
efficiency enhancements.

Change-Id: Ia60e1ea888457fa1c0c0273cdd4b0180f0a87abf
Co-authored-by: Diep Quynh <remilia.1505@gmail.com>
Signed-off-by: Alexander Winkowski <dereference23@outlook.com>