iio: Declare event_attrs field of iio_info structure as const

The event_attrs field of iio_info structure is only initialized once
whenever an object of iio_info is created. After that this field
is never modified again anywhere in the kernel. So, declare event_attrs
field of iio_info as a const struct attribute_group.
Checked for occurences throughout the kernel using grep and
coccinelle.
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

include/linux/iio/iio.h

@@ -381,7 +381,7 @@ struct iio_dev;
  **/
 struct iio_info {
 	struct module			*driver_module;
-	struct attribute_group		*event_attrs;
+	const struct attribute_group	*event_attrs;
 	const struct attribute_group	*attrs;
 
 	int (*read_raw)(struct iio_dev *indio_dev,