AP_HAL_Linux: changed ADC logic a bit for Navio 2

- make voltage_average_ratiometric() the same as voltage_average()
- make read_latest() the same as voltage_average()

wip

libraries/AP_HAL_Linux/AnalogIn_Navio2.cpp

@@ -62,7 +62,7 @@ float AnalogSource_Navio2::read_average()
 
 float AnalogSource_Navio2::read_latest()
 {
-    return _value;
+    return voltage_average();
 }
 
 float AnalogSource_Navio2::voltage_average()
@@ -84,12 +84,13 @@ float AnalogSource_Navio2::voltage_average()
 
 float AnalogSource_Navio2::voltage_latest()
 {
+    read_latest();
     return _value;
 }
 
 float AnalogSource_Navio2::voltage_average_ratiometric()
 {
-    return _value;
+    return voltage_average();
 }
 
 AnalogIn_Navio2::AnalogIn_Navio2()