IB/ehca: Misc cpuinit section annotations and #ifdef cleanups

* Replace {un}register_cpu_notifier with {un}register_hotcpu_notifier
  thereby losing a couple of #ifdef HOTPLUG_CPU pairs.
* Move comp_pool_callback_nb declaration to below that of callback
  function so that initialization of .notifier_call and .priority can
  occur at build time itself and not runtime.
* Mark the notifier_block (and callback function, and another static
  function used by it) as __cpuinit{data} for the sake of consistency
  and remove enclosing #ifdef. (This may increase size for modular
  build of this module, however, because these are no longer dropped
  unconditionally now.)

Signed-off-by: Satyam Sharma <satyam@infradead.org>
Acked-by: Joachim Fenkes <fenkes@de.ibm.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>