Staging: iio: Fix type warnings

Signed-off-by: Alan Cox <alan@linux.intel.com>
Cc: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/accel/sca3000_ring.c

@@ -210,7 +210,7 @@ static struct attribute_group sca3000_ring_attr = {
 	.attrs = iio_ring_attributes,
 };
 
-static struct attribute_group *sca3000_ring_attr_groups[] = {
+static const struct attribute_group *sca3000_ring_attr_groups[] = {
 	&sca3000_ring_attr,
 	NULL
 };

drivers/staging/iio/ring_sw.c

@@ -392,7 +392,7 @@ static struct attribute_group iio_ring_attribute_group = {
 	.attrs = iio_ring_attributes,
 };
 
-static struct attribute_group *iio_ring_attribute_groups[] = {
+static const struct attribute_group *iio_ring_attribute_groups[] = {
 	&iio_ring_attribute_group,
 	NULL
 };