EPCS: Free memory?

From the fpga configuration file (.sof) and the Nios firmware file (.elf) you know exactly the epcs space required. The remaining (if any) is free for general purpose use.

Some important points to remind:

- epcs must be erased in blocks (64k if I remember correctly). So your data and firmware must be stored in a separate blocks.

- at the end of used epcs space allow some headroom for future upgrades

- similarly, you must account for extra space if your design provides remote update