staging:iio: Fix mention of INDIO_RING_TRIGGERED to INDIO_BUFFER_TRIGGERED

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/Documentation/trigger.txt

@@ -31,5 +31,5 @@ consumers.
 Trigger Consumers
 
 Currently triggers are only used for the filling of software
-buffers and as such any device supporting INDIO_RING_TRIGGERED has the
+buffers and as such any device supporting INDIO_BUFFER_TRIGGERED has the
 consumer interface automatically created.