iio: Documentation: Add trigger name attribute ABI documentation

This patch adds an entry in ABI Documentation for the name attribute
issued when a trigger is created.

Signed-off-by: Cristina Opriceana <cristina.opriceana@gmail.com>
Acked-by: Daniel Baluta <daniel.baluta@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

Documentation/ABI/testing/sysfs-bus-iio-trigger-sysfs

@@ -9,3 +9,12 @@ Description:
 		automated testing or in situations, where other trigger methods
 		are not applicable. For example no RTC or spare GPIOs.
 		X is the IIO index of the trigger.
+
+What:		/sys/bus/iio/devices/triggerX/name
+KernelVersion:	2.6.39
+Contact:	linux-iio@vger.kernel.org
+Description:
+		The name attribute holds a description string for the current
+		trigger. In order to associate the trigger with an IIO device
+		one should write this name string to
+		/sys/bus/iio/devices/iio:deviceY/trigger/current_trigger.