mv_machine_learning: use reference and vector

mv_machine_learning: use reference and vector

[Issue type] : code clean

Use reference instead of pointer when returning the result to user
and replace the array type of members of object_detection_3d_result_s structure
with vector type.

Change-Id: Ieed3a2d087e617af604f7a42d57d7a78eab0d116
Signed-off-by: Inki Dae <inki.dae@samsung.com>