fix piethernet blocking write return value

libs/main/io_devices/piethernet.cpp

@@ -861,6 +861,7 @@ ssize_t PIEthernet::writeDevice(const void * data, ssize_t max_size) {
 						return -1;
 					}
 				}
+				ret += sr;
 				remain_data += sr;
 				remain_size -= sr;
 			}