betafpv: fix adc channel
//VOLTAGE DIVIDER
#define BATTERYPIN GPIO_Pin_0
#define BATTERYPORT GPIOB
-#define BATTERY_ADC_CHANNEL ADC_Channel_12
+#define BATTERY_ADC_CHANNEL ADC_Channel_8
#ifndef VOLTAGE_DIVIDER_R1
#define VOLTAGE_DIVIDER_R1 10000
