Peter,
Just adding to Victor's reply, section 4.3.3 of the board user's guide indicates the USB port in the board is connected directly to the UART port of the F5438 device. Page 17 of the F5438 device datasheet mentions the device UART can be used to program its flash via the Bootstrap Loader (BSL). This section contains a document reference on how to perform this programming.
Regards,
Rafael