drivers: adc: stm32g0 fix sampling time due to errata sheet

According to the ES0418 about the ADC of the stm32G071
or other stm32g0x devices:
for sampling time set to 1.5 or 3.5 cycles,
the sampling in a single ADC conversion or in the first
conversion of a sequence takes one extra cycle.
Minimizing to 7.5 is fine.

Signed-off-by: Francois Ramu <francois.ramu@st.com>

Author: FRASTM

drivers/adc/adc_stm32.c

@@ -837,6 +837,10 @@ static void adc_stm32_setup_speed(const struct device *dev, uint8_t id,
 	LL_ADC_SetSamplingTimeCommonChannels(adc,
 		table_samp_time[acq_time_index]);
 #elif defined(CONFIG_SOC_SERIES_STM32G0X)
+	/* Errata ES0418 and more: ADC sampling time might be one cycle longer */
+	if (acq_time_index  < 2) {
+		acq_time_index = 2;
+	}
 	LL_ADC_SetSamplingTimeCommonChannels(adc, LL_ADC_SAMPLINGTIME_COMMON_1,
 		table_samp_time[acq_time_index]);
 #else