iio: adc: ad9467: fix scan type sign

According to the IIO documentation, the sign in the scan type should be
lower case. The ad9467 driver was incorrectly using upper case.

Fix by changing to lower case.

Fixes: 4606d0f4 ("iio: adc: ad9467: add support for AD9434 high-speed ADC")
Fixes: ad679712 ("iio: adc: ad9467: add support AD9467 ADC")
Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://lore.kernel.org/r/20240503-ad9467-fix-scan-type-sign-v1-1-c7a1a066ebb9@baylibre.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ad9467.c

@@ -243,11 +243,11 @@ static void __ad9467_get_scale(struct ad9467_state *st, int index,
 }
 
 static const struct iio_chan_spec ad9434_channels[] = {
-	AD9467_CHAN(0, 0, 12, 'S'),
+	AD9467_CHAN(0, 0, 12, 's'),
 };
 
 static const struct iio_chan_spec ad9467_channels[] = {
-	AD9467_CHAN(0, 0, 16, 'S'),
+	AD9467_CHAN(0, 0, 16, 's'),
 };
 
 static const struct ad9467_chip_info ad9467_chip_tbl = {