Move request engine callbacks to req structure

Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>

src/engine/engine_wb.c

@@ -189,10 +189,11 @@ int ocf_write_wb(struct ocf_request *req)
 
 	/* Set resume io_if */
 	req->io_if = &_io_if_wb_resume;
+	req->engine_cbs = &_wb_engine_callbacks;
 
 	/* TODO: Handle fits into dirty */
 
-	lock = ocf_engine_prepare_clines(req, &_wb_engine_callbacks);
+	lock = ocf_engine_prepare_clines(req);
 
 	if (!ocf_req_test_mapping_error(req)) {
 		if (lock >= 0) {