edn_pkg does not exist

[sadjadtu]

Hello.

Inside the prim_edn_req.sv module, there are some ports and signals, types of which are defined from a package named "edn_pkg", while there is no such a package in the repository.

[Rupert Swarbrick]

This module got vendored in from OpenTitan (which has an entropy distribution network, which prim_edn_req connects to).

But the end result is a little silly! I suspect the sensible fix is to move the EDN requestor into the EDN directory (instead of the "prim" directory). After that change, we could re-vendor from OpenTitan and prim_edn_req would vanish from the Ibex repository.