RFR: 8368897: RISC-V: Cleanup RV_EXT_FEATURE_FLAGS & RV_NON_EXT_FEATURE_FLAGS [v4]

[Hamlin Li]

On Thu, 9 Oct 2025 08:31:35 GMT, Hamlin Li <mli at openjdk.org> wrote:

> It doesn't seem to be necessary to have a enabled() check for non-extension features like zicboz_block_size, mvendorid, etc. So we might want to remove this check and give these features a default value (maybe -1 as suggested by @Hamlin-Li).

I can refactor this in another pr. In this one, I'll just focus on 2 simple things: reorder, and move comments close to feature declaration.
Same as the consistent interface of VM_Version.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27562#discussion_r2415989071