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: I010ea89c2cdcc7d091c4842fec706464660efad9
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>