Remove LEDC_BASE_FREQ to calculate duty (#381)

libraries/ESP32/examples/AnalogOut/LEDCSoftwareFade/LEDCSoftwareFade.ino

@@ -28,8 +28,8 @@ int fadeAmount = 5;    // how many points to fade the LED by
 // Arduino like analogWrite
 // value has to be between 0 and valueMax
 void ledcAnalogWrite(uint8_t channel, uint32_t value, uint32_t valueMax = 255) {
-  // calculate duty
-  uint32_t duty = (LEDC_BASE_FREQ / valueMax) * min(value, valueMax);
+  // calculate duty, 8191 from 2 ^ 13 - 1
+  uint32_t duty = (8191 / valueMax) * min(value, valueMax);
 
   // write duty to LEDC
   ledcWrite(channel, duty);