Create a microload that works on the Atlys and Opsis board

[mithro]

Currently microload firmware only works on the Opsis. It loads stuff via the hardware I2C controller with the FPGA emulation something like an EEPROM.

This doesn't work on the Atlys because the FPGA isn't connected to the I2C control lines.

Instead we could use the FIFO interface and a flag IO. The flag pin could also be used for reset.

[mithro]

Probably want the flag IO to be one of the "interrupt" pins.