Partial XIF implementation

[fmme26]

Control logic needs to be developed, XIF coprocessor signals were added to the different modules.

[MikeOpenHWGroup]

Hi @fmme26, thanks for your interest in OpenHW and the CVE2. This is an interesting, and potentially valuable contribution. However, we cannot consider merging it at this time for two reasons:

1. You do not appear to be covered by the Eclipse Contributor Agreement.
2. Neither of the initial or current Project Descriptions and Plans for the CVE2 include the CORE-V-eXtension Interface, so this pull-request is a significant change of scope.

The first issue is trivia to resolve. Click the link above and follow the directions. Important: ensure that the email address you use for the ECA is the same email address associated with your GitHub ID.

The second issue is more complex. If you wish the OpenHW Group to adopt a new feature in an existing core, you will need approval of the Technical Working Group. If you would like to discuss this further, please reach out to me at [email protected].

For now, I will keep this PR open with a DoNotMerge label.