iio:core: Handle error when mask type is not separate

When event spec is shared by multiple channels, which has definition
for mask_shared_by_type, iio_device_register_eventset fails.

For example:
static const struct iio_event_spec iio_dummy_events[] = {
	{
		.type = IIO_EV_TYPE_THRESH,
		.dir = IIO_EV_DIR_RISING,
		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
		.mask_shared_by_type = BIT(IIO_EV_INFO_VALUE),
	}, {
		.type = IIO_EV_TYPE_THRESH,
		.dir = IIO_EV_DIR_FALLING,
		.mask_separate = BIT(IIO_EV_INFO_ENABLE),a
		.mask_shared_by_type = BIT(IIO_EV_INFO_VALUE),
	}
};

If two channels use this event spec, this will result in error.

This change handles EBUSY error similar to iio_device_add_info_mask_type().
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Cc: Stable@vger.kernel.org

drivers/iio/industrialio-event.c

@@ -345,6 +345,9 @@ static int iio_device_add_event(struct iio_dev *indio_dev,
 			&indio_dev->event_interface->dev_attr_list);
 		kfree(postfix);
 
+		if ((ret == -EBUSY) && (shared_by != IIO_SEPARATE))
+			continue;
+
 		if (ret)
 			return ret;