iwlwifi: Don't send host commands on rfkill

This patch prevents sending host commands when rfkill is on

Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>