iio: sensorhub: Add sensorhub bindings

Add sensorhub bindings for sensorhub on Galaxy Gear 2.

Signed-off-by: Karol Wrona <k.wrona@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>