sensor: Remove device open/close callback for G-sensor driver kxtj9

Remove these two callback that device will not powerup when device is
opened, it power on/off state will be controled though device enable node.

Signed-off-by: Figo Wang <figow@codeaurora.org>
Change-Id: I7200c862dec950cb28969f4e646ed6c70a7d16c4