IIO: call sensor hub open close function

Call hid_sensor_hub_device_open when user space opens device and call
hid_sensor_hub_device_close when device is closed. This helps in
saving power.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>