sched: fix rounding error on scaled execution time calculation

It's found that the scaled execution time can be less than its actual time
due to rounding errors.  The HMP scheduler accumulates scaled execution
time of tasks to determine if tasks are in need of up-migration.  But the
rounding error prevents the HMP scheduler from accumulating 100% load which
prevents us from ever reaching an up-migrate of 100%.
Fix rounding error by rounding quotient up.

CRs-fixed: 759041
Change-Id: Ie4d9693593cc3053a292a29078aa56e6de8a2d52
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>