sensord: modify HAL interface for support sensorhub

sensord: modify HAL interface for support sensorhub

* It doesn't need to support multi event types anymore,
  because a sensor has a only 1 event_type in new architecture.
  - removed interface of multi event types.
  - concept of "event type" is not removed completely still because of
    internal API. it will be removed later.
* HAL interface supports multi sensor using get_sensor_list() API.
* memory of sensor_event must be allocated in HAL.
  sensor fw will free this allocated memory.
* refactoring and cleaning the code will be continue.

* sensors will work when that sensor_event_poller patch is applied.

Change-Id: I5c4282d9600a8b05f3b495d764dd28cf56ca356d
Signed-off-by: kibak.yoon <kibak.yoon@samsung.com>