iio: adc: ad7791: remove sample freq sysfs attributes

In the current state, these attributes are broken, because they are
registered already, and the kernel throws a warning.
The first registration happens via the `IIO_CHAN_INFO_SAMP_FREQ` flag from
the `ad_sigma_delta` driver.

In this commit these attrs are removed, and in the following the
IIO_CHAN_INFO_SAMP_FREQ behavior will be implemented, which replaces these
hooks.

This is done to make things a bit easier to review as there is a bit of
overlap in the patch if it's done all at once.

Fixes: a13e831fcaa7 ("staging: iio: ad7192: implement IIO_CHAN_INFO_SAMP_FREQ")

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ad7791.c

@@ -244,58 +244,9 @@ static int ad7791_read_raw(struct iio_dev *indio_dev,
 	return -EINVAL;
 }
 
-static const char * const ad7791_sample_freq_avail[] = {
-	[AD7791_FILTER_RATE_120] = "120",
-	[AD7791_FILTER_RATE_100] = "100",
-	[AD7791_FILTER_RATE_33_3] = "33.3",
-	[AD7791_FILTER_RATE_20] = "20",
-	[AD7791_FILTER_RATE_16_6] = "16.6",
-	[AD7791_FILTER_RATE_16_7] = "16.7",
-	[AD7791_FILTER_RATE_13_3] = "13.3",
-	[AD7791_FILTER_RATE_9_5] = "9.5",
-};
-
-static ssize_t ad7791_read_frequency(struct device *dev,
-	struct device_attribute *attr, char *buf)
-{
-	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
-	struct ad7791_state *st = iio_priv(indio_dev);
-	unsigned int rate = st->filter & AD7791_FILTER_RATE_MASK;
-
-	return sprintf(buf, "%s\n", ad7791_sample_freq_avail[rate]);
-}
-
-static ssize_t ad7791_write_frequency(struct device *dev,
-	struct device_attribute *attr, const char *buf, size_t len)
-{
-	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
-	struct ad7791_state *st = iio_priv(indio_dev);
-	int i, ret;
-
-	i = sysfs_match_string(ad7791_sample_freq_avail, buf);
-	if (i < 0)
-		return i;
-
-	ret = iio_device_claim_direct_mode(indio_dev);
-	if (ret)
-		return ret;
-	st->filter &= ~AD7791_FILTER_RATE_MASK;
-	st->filter |= i;
-	ad_sd_write_reg(&st->sd, AD7791_REG_FILTER, sizeof(st->filter),
-			st->filter);
-	iio_device_release_direct_mode(indio_dev);
-
-	return len;
-}
-
-static IIO_DEV_ATTR_SAMP_FREQ(S_IWUSR | S_IRUGO,
-		ad7791_read_frequency,
-		ad7791_write_frequency);
-
 static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("120 100 33.3 20 16.7 16.6 13.3 9.5");
 
 static struct attribute *ad7791_attributes[] = {
-	&iio_dev_attr_sampling_frequency.dev_attr.attr,
 	&iio_const_attr_sampling_frequency_available.dev_attr.attr,
 	NULL
 };