Today's implementation allow LED to blink based on the traffic
condition. We introduce an additional LED mode that reflects the RF
state.

The supported LED modes after this are:
  IWL_LED_BLINK (current/default) - blink rate based on current Tx/Rx
                                    traffic
  IWL_LED_RF_STATE (new) -
    LED OFF: No power/RF disabled, the LED is emitting no light
    LED ON:  Powered/RF enabled, the LED is emitting light
             in a stable non-flashing state.

In order to provide the flexibility to support different LED
behavior per user/system preference we add "led_mode" iwlcore module
parameter.
Signed-off-by: NWey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: NReinette Chatre <reinette.chatre@intel.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>