samd: Reduce a further 48 bytes for non-full builds

Another reduction of -48 bytes can be had if the fine calculation
step is skipped. The worst difference compared to the old reference
code with my calibration values in the 0° to 60° was 2°C,
and the difference at 25°C is 1°C.

The final size decrease for non-full builds like Trinket M0 is 268
bytes.

Author: jepler

ports/atmel-samd/common-hal/microcontroller/Processor.c

@@ -122,8 +122,6 @@ STATIC float calculate_temperature(uint16_t raw_value) {
     int VADCR = ADCR * INT1VR;
     int VADCH = ADCH * INT1VH;
 
-    int INT1VM;    /* Voltage calculation for reality INT1V value during the ADC conversion */
-
     int VADC = raw_value * 1000;
 
     // Hopefully compiler will remove common subepxressions here.
@@ -134,7 +132,10 @@ STATIC float calculate_temperature(uint16_t raw_value) {
     // Coarse Temp Calculation by assume INT1V=1V for this ADC conversion
     int coarse_temp = tempR + (tempH - tempR) * (VADC - VADCR) / (VADCH - VADCR);
 
+    #if CIRCUITPY_FULL_BUILD
     // Calculation to find the real INT1V value during the ADC conversion
+    int INT1VM;    /* Voltage calculation for reality INT1V value during the ADC conversion */
+
     INT1VM = INT1VR + (((INT1VH - INT1VR) * (coarse_temp - tempR)) / (tempH - tempR));
 
     int VADCM = raw_value * INT1VM;
@@ -143,6 +144,9 @@ STATIC float calculate_temperature(uint16_t raw_value) {
     float fine_temp = tempR + (((tempH - tempR) * (VADCM - VADCR)) / (VADCH - VADCR));
 
     return fine_temp / 10;
+    #else
+    return coarse_temp / 10.;
+    #endif
 }
 #endif // SAMD21