staging:iio:ad2s90: Check channel type at read_raw

This patch adds a channel type check at the beginning of the
ad2s90_read_raw function. Since ad2s90 has only one channel, it just
checks if the given channel is the expected one and if not, return
-EINVAL.

Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/staging/iio/resolver/ad2s90.c

@@ -34,6 +34,9 @@ static int ad2s90_read_raw(struct iio_dev *indio_dev,
 	int ret;
 	struct ad2s90_state *st = iio_priv(indio_dev);
 
+	if (chan->type != IIO_ANGL)
+		return -EINVAL;
+
 	switch (m) {
 	case IIO_CHAN_INFO_SCALE:
 		/* 2 * Pi / 2^12 */