sched: window-stats: update during migration and earlier at wakeup

During migrations accounting needs to be done in set_task_cpu() to
subtract the task activity from the source CPU and add it to the
destination CPU. This accounting will require that the task's window
based load statistics be up to date.

Unfortunately, the window-based statistics cannot always be updated in
set_task_cpu() because they are already being updated in the wakeup
path. We cannot update the statistics solely in the wakeup path
because not all wakeups are migrations. Those non-migrating wakeups
will not enter set_task_cpu().

To ensure the window-based stats are always updated for both wakeup
migrations and regular migrations, they are updated earlier in the
wakeup path, and also updated in set_task_cpu if the task is already
runnable (this ensures it is not a wakeup migration, but a regular
migration).

Change-Id: Ib246028741d0be9bb38ce93679d6e6ba25b10756
Signed-off-by: Steve Muckle <smuckle@codeaurora.org>
Signed-off-by: Srivatsa Vaddagiri <vatsa@codeaurora.org>