Add getter function for cache->device->concurrency.cache_line

The purpose of this change is to facilitate unit testing.

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

src/engine/engine_pt.c

@@ -34,7 +34,7 @@ static void _ocf_read_pt_complete(struct ocf_request *req, int error)
 	/* Complete request */
 	req->complete(req, req->error);
 
-	ocf_req_unlock_rd(req->cache->device->concurrency.cache_line, req);
+	ocf_req_unlock_rd(ocf_cache_line_concurrency(req->cache), req);
 
 	/* Release OCF request */
 	ocf_req_put(req);