The GPIO pins are in one of the 4 ports of the 8051 architecture, cannot exaclty remember which port, but you can easily doublecheck that in the datasheet
Added after 3 minutes:
to upload the firmware, you can use the TI's apploader driver, or you can use the IIC eeprom for the production version of your system.
I'm still looking for the TI's reference firmware for the TUSB3410...