drivers: adc: nrf: align to non-gain configuration

Some nRF devices do not allow to configure gain.

Signed-off-by: Nikodem Kastelik <nikodem.kastelik@nordicsemi.no>

Author: nika-nordic

drivers/adc/adc_nrfx_saadc.c

@@ -65,7 +65,9 @@ static const uint32_t saadc_psels[NRF_SAADC_DVDD + 1] = {
 	[NRF_SAADC_AIN6] = NRF_PIN_PORT_TO_PIN_NUMBER(4U, 1),
 	[NRF_SAADC_AIN7] = NRF_PIN_PORT_TO_PIN_NUMBER(3U, 1),
 	[NRF_SAADC_VDD]  = NRF_SAADC_INPUT_VDD,
+#if defined(NRF_SAADC_INPUT_AVDD)
 	[NRF_SAADC_AVDD] = NRF_SAADC_INPUT_AVDD,
+#endif
 	[NRF_SAADC_DVDD] = NRF_SAADC_INPUT_DVDD,
 };
 #endif
@@ -231,6 +233,7 @@ static int adc_nrfx_channel_setup(const struct device *dev,
 		return -EINVAL;
 	}
 
+#if NRF_SAADC_HAS_CH_GAIN
 	switch (channel_cfg->gain) {
 #if defined(SAADC_CH_CONFIG_GAIN_Gain1_6)
 	case ADC_GAIN_1_6:
@@ -284,6 +287,9 @@ static int adc_nrfx_channel_setup(const struct device *dev,
 		break;
 #endif
 	default:
+#else
+	if (channel_cfg->gain != ADC_GAIN_1) {
+#endif /* defined(NRF_SAADC_HAS_CH_GAIN) */
 		LOG_ERR("Selected ADC gain is not valid");
 		return -EINVAL;
 	}