RFR: 8369685: RISC-V: refactor code related to RVFeatureValue::enabled [v2]

[Hamlin Li]

> Hi,
> Can you help to review this patch?
> @RealFYang 
> 
> Original discussion is here: https://github.com/openjdk/jdk/pull/27562#discussion_r2415984981.
> Although seems we can not remove it, but we can still remove some of the redundant check like `mvendorid.enabled()`.
> And also do some simple refactoring related to enable/disable/enabled and so on.
> 
> Thanks

Hamlin Li has updated the pull request incrementally with one additional commit since the last revision:

  review

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/27771/files
  - new: https://git.openjdk.org/jdk/pull/27771/files/48c78ad9..50bc9bb2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27771&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27771&range=00-01

  Stats: 19 lines in 2 files changed: 3 ins; 9 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/27771.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27771/head:pull/27771

PR: https://git.openjdk.org/jdk/pull/27771