iio: adc: ad7292: remove unneeded spi_set_drvdata()

This seems to have been copied from a driver that calls spi_set_drvdata()
but doesn't call spi_get_drvdata().
Setting a private object on the SPI device's object isn't necessary if it
won't be accessed.
This change removes the spi_set_drvdata() call.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Tested-by: Marcelo Schmitt <marcelo.schmitt1@gmail.com>
Reviewed-by: Marcelo Schmitt <marcelo.schmitt1@gmail.com>
Link: https://lore.kernel.org/r/20201119142720.86326-1-alexandru.ardelean@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ad7292.c

@@ -276,8 +276,6 @@ static int ad7292_probe(struct spi_device *spi)
 		return -EINVAL;
 	}
 
-	spi_set_drvdata(spi, indio_dev);
-
 	st->reg = devm_regulator_get_optional(&spi->dev, "vref");
 	if (!IS_ERR(st->reg)) {
 		ret = regulator_enable(st->reg);