iwlwifi: remove obsoleted host command

"RADAR_NOTIFICATION" host command is not used and not supported by uCode,
remove it from driver code.

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>