AP_Notify: use NTF_BUZZ_ENABLE to disable tonealarm

libraries/AP_Notify/Buzzer.cpp

@@ -33,6 +33,9 @@ extern const AP_HAL::HAL& hal;
 
 bool Buzzer::init()
 {
+    if (pNotify->buzzer_enabled() == false) {
+        return false;
+    }
 #if defined(HAL_BUZZER_PIN)
     _pin = HAL_BUZZER_PIN;
 #else

libraries/AP_Notify/ToneAlarm.cpp

@@ -93,6 +93,9 @@ const AP_ToneAlarm::Tone AP_ToneAlarm::_tones[] {
 
 bool AP_ToneAlarm::init()
 {
+    if (pNotify->buzzer_enabled() == false) {
+        return false;
+    }
     if (!hal.util->toneAlarm_init()) {
         return false;
     }