core_ctl: Harden the adjustment_possible() check for unisolation

When the need for CPUs is more than the active CPUs and there are some
isolated CPUs, we wakeup the core_ctl thread to unisolate some CPUs.
The core_ctl task can't unisolate any CPU if all of them are isolated
by other clients. Track the number of isolated CPUs by core_ctl and
wakeup the core_ctl task when adjustment is really possible.

Change-Id: I11ef10860532df25cbde572aabd4b925320db8fe
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>