The threshold callbacks are installed before the initialization of the
online cpus has succeeded and removed after the teardown has been
done. That's both wrong as callbacks might be invoked into a half
initialized or torn down state.

Move them to the proper places: Last in init() and first in exit().

While at it shorten the insane long and horrible named function names.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>