msm: thermal: Use the new device framework API

Modify the thermal driver to use the new device framework API
instead of the cpu_up/cpu_down call. The new framework API, will
keep the online/offline value reported in sysfs in sync with the
actual core status. Bypassing this framework by using cpu_up/cpu_down
will not update the value reported in the sysfs.

Also protect the device framework APIs with device hotplug lock to
provide mutual exclusion between multiple drivers using the same API.

Change-Id: I55e578ec6afdcdd7537ff7afc411bd03f277d59e
Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>