Fix efinity tool

[louiecaulfield]

The top level of the efinity tool is missing, making fusesoc not find the tool.

This fixes it.

[olofk]

This is actually by design. Efinity is only implementing the new Flow API rather than the old Tool API. There are a number of benefits to this new API and I have been writing a bit about it e.g. here but I'm aware it could have been better communicated.

Basically, what you need to do is to add a key flow : efinity to your target, and then specify all your tool- and flow-specific options under the flow_options key. Adding the flow key will tell FuseSoC to use the new flow API which ignores the default_tool and tool_options keys.

I was hoping to have all tools ported to the new flow API by now, but it has taken much longer than expected due to limited time to work on this.