iwlwifi: add notification infrastructure to iwlcore

This patch add notification function to be called by low level
iwl driver to notify iwlcore with current state. This function
will call iwlcore subsystem with the new state. This will
help make the code more consistent and easy to extend. For example
the rf-kill need to know when the driver in init, start, stop or
remove state. Instead doing the same call in 3945 and 4965, we
just do it from this function.

Signed-off-by: Mohamed Abbas <mabbas@linux.intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>