core_ctl: remove "cpus" sysfs file that prints CPU online status

core_ctl module no longer hotplug the CPUs. Hence remove the
/sys/devices/system/cpu/cpuX/core_ctl/cpus file interface which
pints the online/offline state of all CPUs in the cluster.

The global_state file interface can still be used to know all
the state information about all CPUs. Replace "Active" with
"Isolated" string in this file output. Otherwise we see that
an offline CPU as active.

Change-Id: Id6ffb1c3ddfe85cf34ab670ceea8b53e5b2f60e2
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>