RFR: 8359105: RISC-V: No need for acquire fence in safepoint poll during JNI calls

[Anjian Wen]

backport of acquire fence removal in safepoint poll during JNI calls as aarch64

At least in jdk11, when comes to safepoint::end, it will invoke SafepointMechanism::disarm_local_poll to change the polling_word_offset, which may cause a race when thread come to visit polling_word_offset in native_trans state, so we use acquire fence.

Since the disarm_local_poll has been removed from SafepointSynchronize::end, Thread disarm itself in 
JavaThread::check_special_condition_for_native_trans when trans from native. it seems that there is no need for acquire fence.

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

Commit messages:
 - RISC-V: No need for acquire fence in safepoint poll during JNI calls

Changes: https://git.openjdk.org/jdk/pull/25709/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25709&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8359105
  Stats: 18 lines in 2 files changed: 0 ins; 14 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/25709.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25709/head:pull/25709

PR: https://git.openjdk.org/jdk/pull/25709