RFR: 8316592: RISC-V: implement poly1305 intrinsic [v9]

[ArsenyBochkarev]

On Tue, 14 Nov 2023 15:15:54 GMT, ArsenyBochkarev <duke at openjdk.org> wrote:

>> Are there any restrictions on the value of U_1HI?
>
> Ohh, it looks like I completely missed the `U_1HI` too, sorry. Let's do a two-step reduce then

Done.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16417#discussion_r1392765793