sched: handle frequency alert notifications better

The load reporting during frequency alert notifications is broken under
load aggregation. When aggregation is enabled, the total group busy
time is accounted towards the maximum busy CPU of a frequency domain.
If this CPU has a notification pending, it's group busy time alone is
accounted and other CPU's group busy time is completely ignored.
Similarly if any CPU other than maximum busy CPU has a pending
notification, its group busy time is accounted twice.

Maintain the frequency alert notification flag per frequency domain.
When the notification is pending, don't clip the load to 100% @ fur
for any of the CPUs in the frequency domain.

Change-Id: Iebc7d74d6fafa20430fa1c7d80f34a6ab198832d
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>