sched: modify BUSY_LOAD_FACTOR

Reduces the factor from 50% to 10% such that
sched_get_cpu_last_busy_time() can return the
last time stamp when a given CPU is busy with
more than 2 runnable tasks or has load greater
than the 10% of it's max capacity.

Change-Id: I77bba878b676ebeb418a9e64ab566c0b107666b4
Signed-off-by: Dilip Gudlur <dgudlur@codeaurora.org>