RFR: 8294087: RISC-V: Refactor instruction alignment assertions

Wed Sep 21 04:02:28 UTC 2022

This is a trivial refactoring for some instruction alignment assertions. Due to the fact that the `assert (__ pc() % 4 == 0)` is getting used more, this small patch is extracted first to simplify code reviewing.
This patch doesn't change the code behavior.
Tested hotspot tier1 and tier2 together with other patches on QEMU.

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Commit messages:
 - RISC-V: Refactor instruction alignment assertions

Changes: https://git.openjdk.org/jdk/pull/10370/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10370&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8294087
  Stats: 14 lines in 5 files changed: 10 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/10370.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10370/head:pull/10370

PR: https://git.openjdk.org/jdk/pull/10370