Add removeAllPins to HwPWM instance

Given that no function exists to enumerate added pins, this allows for the HwPWM instance to be completely reset.

Author: jgartrel

cores/nRF5/HardwarePWM.cpp

@@ -205,6 +205,15 @@ bool HardwarePWM::removePin(uint8_t pin)
   return true;
 }
 
+bool HardwarePWM::removeAllPins(void)
+{
+  for(int ch=0; ch<MAX_CHANNELS; ch++)
+  {
+    _set_psel(ch, 0xFFFFFFFFUL);
+  }
+  return true;
+}
+
 bool HardwarePWM::writeChannel(uint8_t ch, uint16_t value, bool inverted)
 {
   VERIFY( ch < MAX_CHANNELS );

cores/nRF5/HardwarePWM.h

@@ -94,6 +94,9 @@ class HardwarePWM
     // Remove a pin from PWM module
     bool removePin  (uint8_t pin);
 
+    // Remove all pins from PWM module
+    bool removeAllPins (void);
+
     // Get the mapped channel of a pin
     int  pin2channel(uint8_t pin) const
     {