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_rd.c

@@ -24,8 +24,8 @@
 
 static void _ocf_read_generic_hit_complete(struct ocf_request *req, int error)
 {
-	struct ocf_cache_line_concurrency *c =
-			req->cache->device->concurrency.cache_line;
+	struct ocf_cache_line_concurrency *c = ocf_cache_line_concurrency(
+			req->cache);
 
 	if (error)
 		req->error |= error;