IIO: Documentation: Add ABI documentatio for gyro quadrature correction

From: Cliff Cai <cliff.cai@analog.com>

Add ABI documentation for gyro quadrature correction.
Signed-off-by: Cliff Cai <cliff.cai@analog.com>
Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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

@@ -698,3 +698,10 @@ Description:
 		with all _en attributes to establish which channels are present,
 		and the relevant _type attributes to establish the data storage
 		format.
+
+What:		/sys/bus/iio/devices/deviceX/gyro_z_quadrature_correction_raw
+KernelVersion:	2.6.38
+Contact:	linux-iio@xxxxxxxxxxxxxxx
+Description:
+		This attribute is used to read the amount of quadrature error
+		present in the device at a given time.