🐛 STM32 ADC followup (#22798)

Marlin/src/HAL/LPC1768/HAL.h

 
 using FilteredADC = LPC176x::ADC<ADC_LOWPASS_K_VALUE, ADC_MEDIAN_FILTER_SIZE>;
 extern uint32_t HAL_adc_reading;
-[[gnu::always_inline]] inline void HAL_start_adc(const pin_t pin) {
+[[gnu::always_inline]] inline void HAL_adc_start_conversion(const pin_t pin) {
   HAL_adc_reading = FilteredADC::read(pin) >> (16 - HAL_ADC_RESOLUTION); // returns 16bit value, reduce to required bits
 }
-[[gnu::always_inline]] inline uint16_t HAL_read_adc() {
+[[gnu::always_inline]] inline uint16_t HAL_adc_get_result() {
   return HAL_adc_reading;
 }
 
 #define HAL_adc_init()
 #define HAL_ANALOG_SELECT(pin) FilteredADC::enable_channel(pin)
-#define HAL_START_ADC(pin)     HAL_start_adc(pin)
-#define HAL_READ_ADC()         HAL_read_adc()
+#define HAL_START_ADC(pin)     HAL_adc_start_conversion(pin)
+#define HAL_READ_ADC()         HAL_adc_get_result()
 #define HAL_ADC_READY()        (true)
 
 // Test whether the pin is valid

Marlin/src/HAL/STM32F1/HAL.cpp

       case POWER_MONITOR_VOLTAGE_PIN: pin_index = POWERMON_VOLTS; break;
     #endif
   }
-  HAL_adc_result = (HAL_adc_results[(int)pin_index] >> 2) & 0x3FF; // shift to get 10 bits only.
+  HAL_adc_result = HAL_adc_results[(int)pin_index] >> (12 - HAL_ADC_RESOLUTION); // shift out unused bits
 }
 
 uint16_t HAL_adc_get_result() { return HAL_adc_result; }