RFR: 8339992: RISC-V: some minor improvements of base64_vector_decode_round

[Fei Yang]

On Wed, 18 Sep 2024 12:57:41 GMT, Hamlin Li <mli at openjdk.org> wrote:

> Hi,
> Can you help to review this simple improvement?
> Thanks.

Looks good. Thanks for making this change.

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Marked as reviewed by fyang (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/21059#pullrequestreview-2312803864