sched: rt: Fix double accounting of cpu util in task placement decision

In RT energy aware task placement, cpu utilization is double accounted
to check whether cpu would be overutilized for given task or not.

Fix the double accounting the cpu util.

Change-Id: Id51dd6c952126b870942746c0408fa387ec3bfb1
Signed-off-by: Lingutla Chandrasekhar <clingutla@codeaurora.org>