[riscv-port-jdk17u:riscv-port] RFR: 8295396: RISC-V: Cleanup useless CompressibleRegions

[Xiaolin Zheng]

Backport `8295396: RISC-V: Cleanup useless CompressibleRegions`.

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

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Commit messages:
 - 8295396: RISC-V: Cleanup useless CompressibleRegions

Changes: https://git.openjdk.org/riscv-port-jdk17u/pull/31/files
 Webrev: https://webrevs.openjdk.org/?repo=riscv-port-jdk17u&pr=31&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8295396
  Stats: 68 lines in 2 files changed: 0 ins; 68 del; 0 mod
  Patch: https://git.openjdk.org/riscv-port-jdk17u/pull/31.diff
  Fetch: git fetch https://git.openjdk.org/riscv-port-jdk17u.git pull/31/head:pull/31

PR: https://git.openjdk.org/riscv-port-jdk17u/pull/31