msm: rq_stats: Disable hotplug and stats by default

Userspace closed source mpdecision binary is nessecary for PowerHAL to work.
As it depends on rq_stats, let's at least disable hotplugging and stats
collection by default. /sys/devices/system/cpu/cpu0/rq-stats/hotplug_disable
is now writable, so hotplug can be reenabled.

Also, add some bits related to current cpu policy.

Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
Signed-off-by: Stefanescu Cristian <howerkraft@gmail.com>
msm: msm_rq_stats: Add proper attribute to enable hotplug

* hotplug_disable attribute resets when device suspend and
  sets when device resumes.
* Thereby, the value is dynamic. Perhaps, this value is read
  by userspace, so we don't want to mess with it further.
* Restore hotplug_disable to original format of read-only.
* Introduce hotplug_enable attribute which will do the job.
* We have "enable" attribute for other hotplug drivers, so
  this implementation aligns with them.

Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
Signed-off-by: Stefanescu Cristian <howerkraft@gmail.com>