core_ctl: Consider high irq loaded CPU as busy

Currently a CPU is considered as busy if it's utilization in
the last window exceeds busy threshold. A CPU loaded with
hardirqs/softirqs does not necessarily have high utilization.
Isolating such CPUs may hurt performance as it involves waking
up the CPU frequently from deep c-state. Prevent isolating
high irq loaded CPUs by considering them as busy.

Change-Id: I169b69f6003eb59a126c8a16b67b65be2aa7af40
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>