Documentation: iio: fix typo in triggered-buffers example

In the "IIO triggered buffer setup" example, iio_triggered_buffer_setup()
is called with "sensor_iio_polfunc" (single 'l') while the function is
defined and later referenced as "sensor_iio_pollfunc" (double 'l'). Fix
the misspelling so the example is consistent.

Signed-off-by: Stepan Ionichev <sozdayvek@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Reviewed-by: Joshua Crofts <joshua.crofts1@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

Author: root3315

Documentation/driver-api/iio/triggered-buffers.rst

@@ -43,7 +43,7 @@ A typical triggered buffer setup looks like this::
     }
 
     /* setup triggered buffer, usually in probe function */
-    iio_triggered_buffer_setup(indio_dev, sensor_iio_polfunc,
+    iio_triggered_buffer_setup(indio_dev, sensor_iio_pollfunc,
                                sensor_trigger_handler,
                                sensor_buffer_setup_ops);