sched/fair: Always wake up on waker cpu for sync wakeups

It is beneficial for performance for tasks that are woken up with sync
flag set to run on the same CPU as the waker.

Change-Id: I1210d59c346b1ed5dfac8a62cf4b0b05c78dc093
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>