[riscv-port-jdk17u:riscv-port] RFR: 8285699: riscv: Provide information when hitting a HaltNode

[Xiaolin Zheng]

Backport one Yadong's patch, which can cleanup some RVC things.

Tested along with other patches, hotspot tier1~4 with fastdebug build.

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Commit messages:
 - 8285699: riscv: Provide information when hitting a HaltNode

Changes: https://git.openjdk.org/riscv-port-jdk17u/pull/21/files
 Webrev: https://webrevs.openjdk.org/?repo=riscv-port-jdk17u&pr=21&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8285699
  Stats: 98 lines in 9 files changed: 45 ins; 39 del; 14 mod
  Patch: https://git.openjdk.org/riscv-port-jdk17u/pull/21.diff
  Fetch: git fetch https://git.openjdk.org/riscv-port-jdk17u.git pull/21/head:pull/21

PR: https://git.openjdk.org/riscv-port-jdk17u/pull/21