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>