Add support for HW version recognition
Issue #1519 will result in introducing additional input to the FPGA. This new I/O will allow the gateware to identify the version of the PCB it is running on.
The reason for this is to protect version 2.1 boards from running potentially damaging functionality (high frequency operation) available in release 4 of the gateware.
Therefore high frequency features of release 4 of the gateware should only be enabled if the PCB version is v4 or higher.