[jdk21u-dev] RFR: 8339248: RISC-V: Remove li64 macro assembler routine and related code

[Gui Cao]

Hi, The same issue also exists in jdk21u-dev. So I would like to backport [JDK-8339248](https://bugs.openjdk.org/browse/JDK-8339248) to jdk21u-dev. with this patch ,it will save us some unnecessary runtime checks. RISC-V specific change, risk is low.

### Testing
- [x] Run hotspot:tier1 tests on SOPHON SG2042 (fastdebug)

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Commit messages:
 - Backport 8339248: RISC-V: Remove li64 macro assembler routine and related code

Changes: https://git.openjdk.org/jdk21u-dev/pull/953/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=953&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339248
  Stats: 111 lines in 4 files changed: 0 ins; 111 del; 0 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/953.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/953/head:pull/953

PR: https://git.openjdk.org/jdk21u-dev/pull/953