adjust adc for rak11310 devices (#3698)

variants/rak11310/variant.h

@@ -14,7 +14,7 @@
 #define BATTERY_PIN 26
 #define BATTERY_SENSE_RESOLUTION_BITS ADC_RESOLUTION
 // ratio of voltage divider = 3.0 (R17=200k, R18=100k)
-#define ADC_MULTIPLIER 3.1 // 3.0 + a bit for being optimistic
+#define ADC_MULTIPLIER 1.84
 
 #define DETECTION_SENSOR_EN 28
 
@@ -47,4 +47,4 @@
 // DIO2 controlls an antenna switch and the TCXO voltage is controlled by DIO3
 #define SX126X_DIO2_AS_RF_SWITCH
 #define SX126X_DIO3_TCXO_VOLTAGE 1.8
-#endif
+#endif