Add support for adaq776x-1 series and add missing features

drivers/iio/adc/ad7768-1.c

@@ -1415,6 +1415,15 @@ static int ad7768_probe(struct spi_device *spi)
 		return -ENOMEM;
 
 	st = iio_priv(indio_dev);
+	/*
+	* The ADC SDI line must be kept high when
+	* data is not being clocked out of the controller.
+	* Request the SPI controller to make MOSI idle high.
+	*/
+	spi->mode |= SPI_MOSI_IDLE_HIGH;
+	ret = spi_setup(spi);
+	if (ret < 0)
+		return ret;
 	st->spi = spi;
 
 	st->regulator = devm_regulator_get(&spi->dev, "vref");