QCamera2: Fix a minor bug during camera open

- The function table pointer returned during
  subsequent calls to 'camera_open' is invalid.

Change-Id: I1dbf7afa90416aa5db41cb788d8affef22cce03f
diff --git a/camera/QCamera2/stack/mm-camera-interface/src/mm_camera_interface.c b/camera/QCamera2/stack/mm-camera-interface/src/mm_camera_interface.c
index e85d71b..3919fc4 100644
--- a/camera/QCamera2/stack/mm-camera-interface/src/mm_camera_interface.c
+++ b/camera/QCamera2/stack/mm-camera-interface/src/mm_camera_interface.c
@@ -1336,7 +1336,7 @@
         g_cam_ctrl.cam_obj[camera_idx]->ref_count++;
         pthread_mutex_unlock(&g_intf_lock);
         CDBG("%s:  opened alreadyn", __func__);
-        return &cam_obj->vtbl;
+        return &g_cam_ctrl.cam_obj[camera_idx]->vtbl;
     }
 
     cam_obj = (mm_camera_obj_t *)malloc(sizeof(mm_camera_obj_t));