DE2-115 Development and Education Board --- User guide

There's no point of using any additional serializer/deserializer hardware, since it is easily implementable in FPGA. You can assign almost any FPGA pin to a certain signal. FPGA is not a microcontroller. Microcontroller have hardware dedicated SPI pins. FPGA has no such pins, so You can use (almost) any pin You like for SPI signals. You will later assign a signal to pin when doing FPGA design in Pin Planner.