[HW] Fix VSTU queue overrun (Issue #369)

[sameh-tensorica]

The vstu (Vector Store Unit) module had a bug reported in issue #369 where it would hang if its instruction queue became full of in-flight issued instructions. This occurred because the pointer-based retirement logic ( issue_pnt != commit_pnt ) erroneously returned false when the circular buffer pointers overlapped.

Changelog

Fixed

• This PR replaces the pointer comparison with a check against the vinsn_commit_valid signal, which correctly identifies when instructions are pending in the queue regardless of the full state.

Added

• A regression test case (TEST_CASE20) has been added to vse32.c to reproduce the hang by filling the queue with several single-element stores.

Checklist

• Automated tests pass
• Changelog updated
• Code style guideline is observed

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