iio: add struct declaration for iio types

Add struct for iio type arrays such as IIO_AVAIL_LIST which can be used
instead of int arrays.
Signed-off-by: Gerald Loacker <gerald.loacker@wolfvision.net>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20221201072220.402585-2-gerald.loacker@wolfvision.netSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

include/linux/iio/iio.h

@@ -381,6 +381,11 @@ s64 iio_get_time_ns(const struct iio_dev *indio_dev);
 
 #define INDIO_MAX_RAW_ELEMENTS		4
 
+struct iio_val_int_plus_micro {
+	int integer;
+	int micro;
+};
+
 struct iio_trigger; /* forward declaration */
 
 /**