Clone 40s-dv (Delete 40s directory)

[silabs-robin]

This PR deletes cv32e40s/*.

---

Overview:

After openhwgroup/cv32e40s-dv#3, the external "dv" repo can replace the directory cv32e40s/.
(Just like it was done for the x.)

The core-specific directories in core-v-verif (i.e. cv32e40s/ and cv32e40x/) will be empty, except for a README with instructions for getting the actual content.

---

Changes:

• bin/clonetb gets new flags, to help clone cv32e40s-dv.
• cv32e40s/README.md just explains how to use bin/clonetb.
• cv32e40s/* is otherwise purged.

---

Rationale:

This was already done for the X, because 1) it significantly eases merging S->X, and 2) it reduces the size of core-v-verif itself (so it just containts common code, libraries, agents, etc).

The reason for doing it on the S as well is because 1) it makes the system symmetrical (both cores have a *-dv repo), and 2) merging will be even easier, 3) dealing with smaller repos are easier.

We already have the cv32e40s-dv repo established, and half-way up to date, and soon it is full-way up to date.

---

Reviewing:

Evaluate the "Changes:" above.

If you want to run hello world:
Clone this PR's branch.
See the instructions in cv32e40s/README.md but use clonetb like it was done in openhwgroup/cv32e40s-dv#3.
Then run hello world as normal.

[silabs-robin]

There should be an -s flag too! ("known stable hash".)

But I want it to point to the merge-commit from openhwgroup/cv32e40s-dv#3 after that PR is merged.

[silabs-robin]

Hi, @MikeOpenHWGroup, @silabs-hfegran, @silabs-krdosvik.
This PR is in draft, but only because it is pending on a different PR to be merged.
Hence, I am requesting an early review, to inspect the principal changes of this PR.

[silabs-krdosvik]

Do you plan to change the merge.sh script: https://github.com/openhwgroup/core-v-verif/blob/cv32e40x/dev/bin/merge.sh, at least I think it would need a change, or be deleted to avoid confusion.

Otherwise, looks good.

[silabs-robin]

Do you plan to change the merge.sh script: https://github.com/openhwgroup/core-v-verif/blob/cv32e40x/dev/bin/merge.sh, at least I think it would need a change, or be deleted to avoid confusion.

(Moving this to a thread, to keep related comments bundled together, and to make it resolveable. @silabs-krdosvik )

Yes, that should be changed as well. Good point.

It should be easy?
Where git subtree is used, we can simply add a remote to the cv32e40s-dv repo instead.
Then everything else should work as before.

Do you think it should be done as part of this PR, or could it wait until later?
I also plan to merge cv32e40s-dv -> cv32e40x-dv, so at that time the script would be useful again and prompt a change.

[silabs-robin]

The related changes in openhwgroup/cv32e40s-dv#3 have now been merged, so this PR is ready to be reviewed/merged.