AP_Notify: make LED_NTF_LEN changes require a reboot

don't dynamically update LED length

libraries/AP_Notify/AP_Notify.cpp

@@ -188,6 +188,7 @@ const AP_Param::GroupInfo AP_Notify::var_info[] = {
     // @Description: The number of Serial LED's to use for notifications (NeoPixel's and ProfiLED)
     // @Range: 1 32
     // @User: Advanced
+    // @RebootRequired: True
     AP_GROUPINFO("LED_LEN", 9, AP_Notify, _led_len, NOTIFY_LED_LEN_DEFAULT),
 
     AP_GROUPEND

libraries/AP_Notify/SerialLED.cpp

@@ -25,22 +25,10 @@ SerialLED::SerialLED(uint8_t led_off, uint8_t led_bright, uint8_t led_medium, ui
 
 bool SerialLED::hw_init()
 {
-    init_ports();
-    hal.scheduler->register_io_process(FUNCTOR_BIND_MEMBER(&SerialLED::timer, void));
+    enable_mask = init_ports();
     return true;
 }
 
-void SerialLED::timer()
-{
-    WITH_SEMAPHORE(_sem);
-
-    const uint32_t now_ms = AP_HAL::millis();
-    if (now_ms - _last_init_ms >= 1000) {
-        _last_init_ms = now_ms;
-        enable_mask = init_ports();
-    }
-}
-
 bool SerialLED::hw_set_rgb(uint8_t red, uint8_t green, uint8_t blue)
 {
     if (enable_mask == 0) {

libraries/AP_Notify/SerialLED.h

@@ -39,11 +39,5 @@ protected:
 private:
     uint16_t enable_mask;
 
-    // perdiodic tick to re-init
-    uint32_t    _last_init_ms;
-
-    // periodic callback
-    void timer();
-
     HAL_Semaphore _sem;
 };