iwlwifi: fix rfkill memory error

Do not free reference to device twice. After rfkill registration succeeds
we only need to call rfkill_unregister() and not rfkill_free().
Also add some debugging.

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>