hi,
I have quick looked on device you used and found that it contains I2C interface as well. Unfortunatelly, it may not be used for data receiving because EZ-USB supports only bus-master mode.
So what I may suggest. Depend on baudrate of data transfer between MCU and DSP, it may be possible to implement software receive driver. Determine what is the start condition when DSP sends byte(s), connect this signal to any of free interrupt pin (here: IE0...IE6). Then set this interrupt to max. priority. Inside ISR, read input bit stream manualy (better with scheme 2-from-3) and place into memory buffer. Just note that you may not block interrupts in the whole and need to calculate timings very carefully. It may be that this idea does not help if DSP sends data with high rate. So last chance: use external hardware (a shift register and maybe some more hardware or just a PLD) and read its content after it is filled with DSP.

BTW: maybe it is time to use another chip?

Good luck!
Oleg