RFR: 8322817: RISC-V: Eliminate -Wparentheses warnings in riscv code

[Kim Barrett]

Please review this change to eliminate some -Wparentheses warnings. This
involved simply adding a few parentheses to make some implicit operator
precedence explicit.

Testing: Local (linux-x64) cross-build for linux-riscv with this change plus
-Wparentheses enabled and other changes to allow that to work.

Requesting someone from the riscv porters to properly test this.

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Commit messages:
 - fix -Wparentheses warnings in riscv code

Changes: https://git.openjdk.org/jdk/pull/17216/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17216&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8322817
  Stats: 9 lines in 2 files changed: 0 ins; 0 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/17216.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17216/head:pull/17216

PR: https://git.openjdk.org/jdk/pull/17216