ANDROID: sched: Add KConfig option to set ENERGY_AWARE sched feature on

This option defaults the ENERGY_AWARE scheduling feature to true,
as without SCHED_DEBUG set this feature can't be enabled or disabled
via sysctl.

Change-Id: Ibf8e5d9d8aedf5cc8f0ef322279209ca65a9786b
Signed-off-by: Chris Redpath <chris.redpath@arm.com>