sched: WALT: fix potential overflow

Task demand and CPU util are in u64.

Change-Id: If7ec1623e723026d3346201122aab0303a6d2ba2
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>
(cherry picked from commit c8b8c92bbc8954ae18cba7eb0c1f3a06a244129c)
[trivial cherry-pick issues]
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
1 file changed