AP_HAL_AVR: AnalogIn returns new ADCSource each time a channel is requested

* fixes a bug where multiple sources created as pin -1, then change to
  appropriate pin on mavlink messages. Make treat each creation as distinct
  object.

libraries/AP_HAL_AVR/AnalogIn.h

@@ -55,7 +55,6 @@ public:
     AP_HAL::AnalogSource* channel(int16_t n, float prescale);
 
 protected: 
-    static ADCSource* _find_or_create_channel(int16_t num, float scale);
     static ADCSource* _create_channel(int16_t num, float scale);
     static void _register_channel(ADCSource*);
     static void _timer_event(uint32_t);

libraries/AP_HAL_AVR/AnalogIn_Common.cpp

@@ -31,15 +31,6 @@ void AVRAnalogIn::init(void* machtnichts) {
     _register_channel(&_vcc);
 }
 
-ADCSource* AVRAnalogIn::_find_or_create_channel(int16_t pin, float scale) {
-    for(int16_t i = 0; i < _num_channels; i++) {
-        if (_channels[i]->_pin == pin) {
-            return _channels[i];
-        }
-    }
-    return _create_channel(pin, scale);
-}
-
 ADCSource* AVRAnalogIn::_create_channel(int16_t chnum, float scale) {
     ADCSource *ch = new ADCSource(chnum, scale);
     _register_channel(ch);
@@ -121,7 +112,7 @@ AP_HAL::AnalogSource* AVRAnalogIn::channel(int16_t ch, float scale) {
     if (ch == ANALOG_INPUT_BOARD_VCC) {
             return &_vcc;
     } else {
-        return _find_or_create_channel(ch, scale);
+        return _create_channel(ch, scale);
     }
 }