Check all vtype bits in vsetvl

[flaviens]

vsetvl ignored vtype bits above bit 7. Check the full XLEN value. Set vill for unsupported encodings.

Verification: Verilator elaboration.

[Copilot]

Pull request overview

This PR fixes vsetvl vtype decoding/legality by validating the full XLEN-wide vtype encoding instead of only the low 8 bits, and by marking unsupported encodings as illegal via vill.

Changes:

• Treat any nonzero reserved vtype bits ([XLEN-2:8]) as illegal by folding them into vill during CSR decoding.
• For vsetvl, consume the full rs2 (XLEN bits) when updating vtype, and explicitly reject vill/illegal combinations when computing the new vl.
• Document the fix in the changelog.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
hardware/src/ara_dispatcher.sv	Validates full-XLEN vtype for vsetvl and forces vill on unsupported encodings.
CHANGELOG.md	Notes the vsetvl/vtype validation fix under “Fixed”.

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