[LMS] cmd_done toggles with each winternitz round

[ludwigatlubis]

In line 423 of module sha256 the signal hwif_in.intr_block_rf.notif_internal_intr_r.notif_cmd_done_sts.hwset of the hardware interface is set.
This signal is asserted whenever a sha256_core computation finishes, i.e., core_digest_valid is asserted.

From our understanding this should only be the case for sha computations.
For winternitz computations, this signal should only be raised when the last sha computation is finished,
i.e., when the winternitz computation performs the transition to the idle state.

We wrote an assertion for this and it fails.
You can find the fsdb containing the waveform of the counterexample generated by the formal tool attached.

command_done_issue.fsdb.zip