dio: try to correct PPS output.

We have remove all connections (input and output) of first channel to the DIO.
In the future we might re-add the input connection...
general-cores: updating gencores to use wb_streamer
etherbone-core: added as submodule
top: Added Etherbone support.

- Added Etherbone core as wishbone master in top crossbar.
- Added a multiplexer to connect Etherbone and Nic core to wr-core.
- Connected wr-core to Etherbone configuration space to access Etherbone registers.
- wrc.ram: Updated with Etherbone support. (Old: wrc_without_etherbone.ram)