Fix tone after rework of HardwareTimer

When timerTonePinDeinit() is called, it will deinitialize timer.
It is then necessary to recreate HardwareTimer object to initialize timer.
So, when NoTone() is called, without destruct, only pause the timer.
Also when frequency is null just pause the timer.

Author: ABOSTM

Diff for: cores/arduino/Tone.cpp

@@ -81,7 +81,9 @@ static void timerTonePinInit(PinName p, uint32_t frequency, uint32_t duration)
 
   if (frequency <= MAX_FREQ) {
     if (frequency == 0) {
-      timerTonePinDeinit();
+      if (TimerTone != NULL) {
+        TimerTone->pause();
+      }
     } else {
       TimerTone_pinInfo.pin = p;
 
@@ -121,12 +123,13 @@ void tone(uint8_t _pin, unsigned int frequency, unsigned long duration)
 void noTone(uint8_t _pin, bool destruct)
 {
   PinName p = digitalPinToPinName(_pin);
-  if ((p != NC) && (TimerTone_pinInfo.pin == p)) {
-    timerTonePinDeinit();
-
-    if ((destruct) && (TimerTone != NULL)) {
+  if ((p != NC) && (TimerTone_pinInfo.pin == p) && (TimerTone != NULL)) {
+    if (destruct) {
+      timerTonePinDeinit();
       delete (TimerTone);
       TimerTone = NULL;
+    } else {
+      TimerTone->pause();
     }
   }
 }