Add image from a 5A-75E V6.0 board

This board uses a LFE5U-25F-6BG256C chip.
Note, however, that there is also a different "V6.0" board with an FPGA chip in a 381-ball package, different RAM chip and magnetics. See q3k/chubby75#65 for relevant discussion.

Board pinout: https://github.com/q3k/chubby75/blob/master/5a-75e/hardware_V6.0.md