msm: lpm_levels: Allow enable/disable LPM for cpus and clusters

Add sysfs interface to allow/disallow low power modes. Every level
specified in the Devicetree for each cpu and cluster will have an
idle_enabled and suspend_enabled option that controls the availability of
the low power mode for CPUIdle and HOTPLUG/Suspend frameworks.

Change-Id: Ic27f3a586eb9992c611411d2a13365b909ae48a3
Signed-off-by: Praveen Chidambaram <pchidamb@codeaurora.org>