staging:iio:documentation trivial typo fix

Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/Documentation/sysfs-bus-iio

@@ -2,7 +2,7 @@ What:		/sys/bus/iio/devices/deviceX
 KernelVersion:	2.6.35
 Contact:	linux-iio@vger.kernel.org
 Description:
-		Hardware chip or device accessed by on communication port.
+		Hardware chip or device accessed by one communication port.
 		Corresponds to a grouping of sensor channels. X is the IIO
 		index of the device.