iio: hid: fix the retval in gyro_3d_capture_sample

Return value should be zero for success. This was forgotten for timestamp
feature. Verified on RealSense cameras.

Fixes: 4648cbd8 ("iio: hid-sensor-gyro-3d: Add timestamp channel")
Signed-off-by: Dmitry Perchanov <dmitry.perchanov@intel.com>
Link: https://lore.kernel.org/r/7c1809dc74eb2f58a20595f4d02e76934f8e9219.camel@intel.com


Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>